Glossary of Watch Terms & Terminology

Read Our Online Horology Guide to Watch Parts

Glossary of Watch Parts

An alarm is any device that makes an audible signal at a pre-set time. Alarms can be mechanical, like a chime or gong, or electronic, sounded through a speaker.

Any watch that says “adjusted” has simply been tested while being assembled to minimize any timekeeping disruption or loss. Watchmakers typically calibrate timepieces by adjusting to nine parameters: stem up and stem down, stem left and stem right, face down and face up, heat and cold, and isochronism.

An altimeter is a complication on a watch that measures altitude above sea level by calculating changes in barometric pressure.

Amplitude is a measure of how much the balance wheel rotates. The distance of this clockwise and counterclockwise motion is measured in degrees, and is typically higher when a watch is lying flat, in a “dial up” or “dial down” position. Extreme changes in amplitude can indicate problems with the watch’s movement.

Analog Watch
An analog watch features the classic look of hour and minute hands rotating clockwise around the dial, indicating the time of day. As the hands progress, they “reset” at 12-hour intervals, and need a separate indicator to note the difference between AM and PM.

Anchor Escapement
Named for its anchor-like shape, an anchor escapement is typically used in pendulum clocks. As the anchor swings back and forth on a pivot point, the two anchor horns, or pallets, alternately catch and release the teeth on the escape wheel, allowing the calibrated release of energy.

Most often found in higher quality movements, anglage is the precision beveling of an edge of a movement component, such as a bridge. Anglage can be applied mechanically, with an engraver, or with a hand-held file.

Annual Calendar
An annual calendar is a complication that adjusts itself to the different lengths of the months from March through January, but needs to be reset once a year to compensate for February’s shorter length and/or the possibility of leap year.

Applied Indices
Applied indices refers to raised metal numbers or batons that are fashioned separately and then physically attached to the dial.

Art Deco
Art deco is an often revisited design style of the 1920s and ‘30s that is characterized by bold and precise geometric shapes and strong colors. In watchmaking, most tonneau- or barrel-shaped and rectangular watches owe their look to the art deco movement.

Automatic Movement
An automatic movement is one whose mainspring is wound by a mechanism that is activated by the daily movements of the watch wearer’s wrist. A small rotor swings and turns with every movement of the wrist, which turns a gear and ratchets the mainspring gear one click at a time. Most automatic movements have a reserve, allowing the watch to remain wound after a period of inactivity. An automatic watch unworn past the reserve period will have to be manually wound to restart the process.

Auto Repeat Countdown Timer
An auto repeat countdown timer is a countdown timer that resets and restarts itself when the preset time has elapsed. This feature is useful for workout drills or interval training.

Watch Glossary of Terms

Balance Wheel
The balance wheel is the part of a mechanical watch that oscillates back and forth on an axle, and is largely responsible for the precision of the timepiece. Most contemporary watches have balances that oscillate at 21,600 or 28,800 times hour, often appreciated “vph” for “vibrations per hour.”

Balance Spring
Often called a “hairspring” due to it’s fine diameter, the hair-thin balance spring coils and recoils in a way that allows the balance wheel to rotate back and forth, in turn keeping the time accurately.

The barrel is a large, drum-like gear that encases the mainspring and provides power to the watch. The size of the barrel determines how long the power reserve is for a given watch. Some watches feature a double barrel that can allow for an extra long power reserve.

The bezel is the ring around the outside of a watch dial that holds the crystal or glass covering in place. Often made of precious metals, bezels can be either snapped onto the case or screwed into place. Bi-directional rotating bezels are made to rotate in both directions in order to measure elapsed time, distance, or speed.

A watch bracelet is a type of watch band made up of pieces that resemble links in a chain.

The bridge is a narrow, flat piece of metal that is attached to the plate at both ends to form the frame of a watch movement. The bridge is normally drilled with one or more holes that contain the jewels that hold the rotating pivots of the moving parts.

A cabochon is a gem that has been shaped and polished without a faceted face, resulting in a rounded, convex stone. In watchmaking, cabochons are sometimes set on the top of the crown.

Caliber is the name given to a specific watch movement model. Calibers are usually designated by a number or letters and numbers.

Cannon Pinion
The cannon pinion is a post that attaches to the center wheel and comes up through the dial. The minute hand is affixed to it on the dial side, usually by friction, completing the conversion of all the watch’s complex motions into a readable display.

Watch Complications GlossaryCase
The case of the watch is the actual housing of the movement, and can be made of various metals, ceramic, or plastic.

Case Diameter
The diameter of a watch case is measured from one end to the other, excluding the crown or other buttons or plungers.

Case Thickness
The measurement from the base of the watch case to the top of the crystal is the case thickness.

The caseback is the simply the back of the watch that rests against the skin. Often etched with the manufacturer’s name, metal content, and features like water and shock resistance, the caseback completes the movement’s covering. Some casebacks are transparent crystal, allowing a view of the inner working of the timepiece.

Center Wheel
The center wheel is at the center of a watch’s movement, and is driven by the barrel, rotating once each hour. The minute hand is attached to the center wheel on the dial side of the movement by the cannon pinion.

Chapter Ring
A chapter ring is the circle near the edge of a watch dial, and includes the indices for hours and often minutes. The markings on the chapter ring can be widely varied, from Arabic or Roman numerals to lines or batons.

A chime is the sound, often bell-like, that a clock or watch makes as it strikes the hour, half hour, or quarter hour.

Literally a “time writer,” a chronograph is simply a stopwatch complication. Usually activated by one to three buttons, or “pushers,” that start, stop, and reset the function, chronographs do not interfere with the normal functions of the watch. Chronographs sometimes feature sub-registers to track elapsed time in seconds, minutes, or hours.

A chronometer is a precision timepiece that is rated by the Contrôle Officiel Suisse des Chronomètres (COSC). To obtain the certificate, mechanical watches have to be accurate to within -4/+6 seconds when tested at various temperatures and positions over a fifteen day period.

The click is the pawl on the ratchet wheel that holds the ratchet wheel against the force of the mainspring as the watch is being wound. The sound made when winding the watch is the click hitting each tooth of the ratchet wheel.

Column Wheel
The column wheel is a notched, rotating wheel in a chronograph that links to the levers that control the on, off, and reset functions.

Compensation Balance
Used in precision timepieces before modern Nivarox-type balance springs, the compensation balance negates errors that occur as traditional steel balance springs became slightly elastic when exposed to changes in temperature. Compensation balances were traditionally made of laminated brass and steel strips, cut in such a way as to nearly eliminate the temperature induced errors.

A complication is any function on a watch that does more than straightforward timekeeping. The most common complications are calendars and chronographs, but others include moon phase indicators, alarms, repeaters, and even altimeters and tide indicators.

Countdown Timer
A countdown timer is a complication that allows the watch wearer to keep track of a pre-set amount of elapsed time. Often found in yachting watches, many countdown timers feature a warning alarm or alarms at preset periods before the end of the countdown cycle.

The crown is the knob on the outside of the case, used for winding the watch and setting the time. Attached to the end of the winding stem, the crown can often be positioned differently to set different functions.

In watchmaking, the term crystal can refer to two distinct items. In mechanical watches, the crystal refers to the protective cover over the face of the watch. These can be made of glass, plastic, or scratch resistant synthetic sapphire. In a quartz watch, the crystal is the small bit of quartz responsible for timekeeping.

COSC is the acronym for Contrôle Officiel Suisse des Chronomètres, the Swiss agency that tests and certifies Swiss chronometers.

Originally patented by Rolex, a cyclops is a small lens in the watch crystal that magnifies the date display, making it easier to read.

Horology GuideDay/Date Watch
Day/Date watches feature a complication that indicates both the date and the day of the week.

Day/Night Indicator
On a watch with a world time complication, the day/night indicator is a shaded or colored band the shows which time zones are in daylight and which are in darkness.

Dead Seconds
Dead seconds is a complication that indicates the seconds in individual, discrete jumps rather than a continuous sweeping movement. In most watches, the second hand moves with each vibration of the balance wheel, or five times per second for a balance wheel vibrating at 18,000 vibrations per hour. A dead second complication mechanically translates that rate to once per second and moves the seconds hand accordingly.

Deployant Buckle
Invented by Louis Cartier in 1910, the deployant buckle is a hinged watch band fastener that allows the strap or bracelet to be widened for putting on or taking off without unbuckling. While more expensive that a traditional buckle, the deployant buckle is considered safer, easier to use, and more comfortable.

Detent Escapement
An important historical escapement, the detent escapement features a thin blade spring that has a mounted jewel to hold the escape wheel. Unlike a lever escapement, the detent escapement delivers energy directly to the balance by the escape wheel, and requires no oil. Though highly efficient and relatively maintenance free, the escape wheel was susceptible to shock, and could unlock when bumped.

The dial is simply the face of the watch that shows the time and other watch features using hands, markers and other indicators.

Digital watches were first developed in the 1970s, and featured LED displays that show the time in arabic digits instead of the classic hands of a traditional analog watch.

Dual Time
Dual time watches display the time in two different time zones, usually doing so with a sub-dial, twin dial, or an extra hand. This complication was originally intended for pilots and traveling businessmen who regularly move between two time zones.

Ébauche is the name for the basic parts of a watch’s movement that are built for assembly by another watchmaker. In contemporary watchmaking, ébauche refers to all of the movement except the escapement components, whereas in traditional Swiss watchmaking, the watchmaker might obtain the ébauche from one supplier, and other components like the balance spring and escapement from other suppliers before final assembly and calibration. Contrasted today with movements built in-house, ébauche movements are generally less coveted, though certain high quality ébauche movements are sometimes better than those built in-house.

Elapsed Time Rotating Bezel
An elapsed time rotating bezel can be set with the zero on the watch’s minutes or seconds hand, allowing the wearer to read elapsed time off the bezel.

Electroplating is a technique that uses strong electrical current to coat certain watch parts with a thin layer of metal. While done sometimes solely for aesthetic reasons, electroplating can be used to increase wear resistance or add corrosion protection.

An alloy of chromium, manganese, tungsten, steel, and nickel, elinvar is used in balances and hairsprings to make them more resistant to changes in temperature.

Endshake refers to the amount of vertical play a pivot has in a jewel-hole. Some endshake is necessary for the unimpeded motion of the gear train, but too much enshake, which can result from worn jewel holes, may allow the pivot or arbor to shake or wobble.

Equation of Time
Because the earth does not perfectly orbit the sun, there is a difference between apparent solar time and mean solar time. An equation of time complication displays the difference between the two.

Online Watch Glossary of TermsEscapement
The escapement is the mechanism that manages the release of power from the mainspring, translating that rotational energy into lateral movement that can then be regulated by the balance wheel and hairspring. Many types of escapements have been developed throughout history, with today’s most common example being the lever escapement.

Escape Wheel
A major part of the escapement, the escape wheel’s teeth interact with the pallet fork, converting rotational motion into lateral pulses.

Fly-Back Chronograph
A fly-back chronograph is a chronograph, or stopwatch, that can be reset without first being stopped. With a single push of a button, the hand is stopped, returned to zero, and instantly restarted. This complication is often used when timing a sequence of events, like laps in a race.

Also known as a flying seconds hand, a foudroyante is a sub-dial that indicates fractions of a second.

Fourth Wheel
The fourth wheel is a part of the watch’s movement that rotates once per minute. When seconds are displayed in a sub-dial, the fourth wheel pivot is directly attached to the seconds hand.

In watchmaking, frequency refers to how many times the balance wheel vibrates each hour, and is often advertised as a selling point. Common frequencies include 18,000, 21,000, 28,800, and 36,000.

A fusee is a cone-shaped, grooved pulley that was used in mechanical watches up until the early 20th century as a way to compensate for the change in force as the mainspring runs down. The fusee has a cord or chain wrapped around it and attached to the mainspring barrel. As the mainspring winds down, the chain moves to the wider part of the fusee, allowing the drive torque to remain constant.

GMT is the abbreviation for Greenwich mean time, or the time at the Royal Observatory at Greenwich, England. The Royal Observatory is located at the prime meridian, where longitude measures zero, and GMT is a similar ‘zero’ from which time is determined throughout the world. So called “GMT” watches can track Greenwich mean time and another time zone, though in reality they can be set to track any two time zones.

Online Watch DictionaryGear Train
Made up of wheels and pinions, the gear train translates torque from the barrel to the escapement in a multiplying train of gears. As the energy moves outward through the wheels, torque loss is minimized through the use of sapphire jewels at the pivots, and polished, hardened pinions. By utilizing multiple wheels, the gear train allows the watch to run for many hours, and accurately divides that time into hours, minutes, and seconds.

Geneva Seal
Also called a “Geneva Hallmark,” a Geneva seal is a quality assurance seal awarded to watch movements made in the canton of Geneva, Switzerland that meet 12 criteria pertaining to the quality of the movement’s finishing and materials.

Geneva Waves
Geneva waves, also called “Geneva stripes” or “côtes de Genève,” are decorative, stripe-like embellishments on the plates, bridges, and rotors of some watches.

Grande Sonnerie
A grand sonnerie is a complication in a mechanical watch or clock that combines a striking mechanism with a repeater to sound two gongs every quarter hour, one pitch indicating the quarter hour, and another to indicate the hour. For instance, at 4:30, there would be two sounds at one pitch, indicating two 15 minute intervals after the hour, and four sounds at another pitch, indicating the hour. In some instances, the hours can be indicated on demand with the push of a button.

Guilloché is a style of engraved ornamentation that employs precise, repetitive patterns, often resembling interwoven braids or waves, creating an impression of texture. Also known as “engine turning,” genuine guilloché is fashioned with an engraving machine. Less expensive, simulated guilloché can be made with a stamping process.

Hacking Seconds
A watch with “hacking seconds” or “stop seconds” features a seconds hand that stops when the crown is pulled out. A lever or brake stops the balance wheel when the crown is pulled, allowing the watch to be synchronized with another timepiece or reference signal when the crown is pushed back in.

Along with the balance wheel, the hairspring helps regulate a mechanical watch. Traditionally made from either steel or gold, these flat spiral springs are made today from silicon or temperature resistant alloys, and provide a restoring force to the balance wheel that results in a precise oscillations.

A hallmark is a stamp certifying the purity of the gold, silver, or platinum used in jewelry. In watchmaking, the hallmark is stamped on a watch’s case. Other marks may indicate the country and year of manufacture, the maker of the case, and some may show the trademark of the watch company, as well as a reference and serial number.

Hand-Wound Movement
A hand-wound movement, also called a manual-wind movement, is a mechanical movement that requires the mainspring to be wound by turning the crown.

The hands of a watch or clock are used, with the dial, to indicate time. Typically made of thin metal, they can be of many different designs.

Glossary of Watch ComplicationsHorology
Horology is the scientific study of time measurement, which in its purest form would include everything from sundials and hourglasses to atomic clocks and marine chronometers. In contemporary usage, horology generally refers to the study of mechanical timekeeping instruments. “Haute Horlogerie” literally means “high watchmaking,” and is used to describe the finest in mechanical watchmaking.

Hunter Case
Also called a ‘hunting case,’ a hunter case is a pocket watch case which features metal covers on both the front and back of the watch.

Incabloc is a brand of shock absorber used in mechanical watch movements. Utilizing lyre-shaped flat springs, these shock absorbers protect the balance staff and pivots from bumps and other mechanical disturbances.

Derived from the Greek roots iso and chronos, isochronism literally means “in the same time.” In watchmaking, it refers to the property of an oscillator, like a pendulum or balance, that takes the same amount of time to complete a swing regardless of how big the swing happens to be. Since timekeeping at its most basic level is simply counting the swings of an oscillator, if that oscillator is not isochronous, there can be no accurate keeping of time.

In watchmaking, the jewels are not the precious stones that might adorn the watch case or bracelet, but rather small bearings made of synthetic sapphire that support wheel pivots to reduce friction and wear in a watch movement. Set in holes drilled in the movement plate or bridges, most jewels are tiny pierced cylinders, with one concave side to hold oil for the pivot.

Jump Hour/Minutes
Watches that feature a jump hour complication have an hour hand that points directly at the current hour and ‘jumps’ to the next hour when the last second of the current hour is completed. Sometimes indicated with a disk imprinted with numerals rather than hands, jump hour watches can also feature ‘jump minutes.’ an identical complication for indicating minutes.

Key Set
Watches that used a small key instead of a winding crown to set the time are known as key set watches. Key set movements are quite rare in today’s watches, though many antique pocket watches featured them.

Keyless Works
The keyless works is the part of a mechanical watch that allows the movement to be wound and the time set by using the winding stem. Depending on the movement, different stem positions will engage different gear trains in the movement, allowing specific functions to be set independently.

The kind of display used in almost all digital quartz watches is a “liquid crystal display,” abbreviate to LCD.

The display used in early digital quartz watches, LED is the abbreviation for “light emitting diode,” and usually lit up in red with the push of a button

Lever Set
A lever set watch is one in which the crystal is removed to access a small lever for setting the time. Most often used in railroad conductor’s pocket watches, the system was designed to prevent inadvertent time changes that might compromise train safety.

A French unit of measurement used before the adoption of the metric system, the ligne is still used by some French and Swiss watchmakers, mainly to describe the diameter of a watch. One ligne is equal to 2.256 millimeters, and is represented by the triple prime, as in 1’’’.

Watch Parts DictionaryLugs
The lugs on a wristwatch are the extensions on both sides of the case where the bracelet or strap are attached.

Maillechort is an alloy of copper, nickel, and zinc, and is used for movement plates and bridges as an alternative to brass. Also known as German silver, maillechort is named for Maillot and Chorier, who invented the alloy in 1820.

Usually fashioned out of brass or German Silver (Nickel), the mainplate is the foundation of a watch’s movement, and the element upon which the rest of the caliber is fashioned.

The mainspring is a spiral spring, housed in the barrel, that gradually uncoils to provides power to all the functions of a mechanical movement. Wound either manually or by an automatic system, most mainsprings today are made of Nivaflex, a metal alloy that is both elastic and resistant to breakage.

An abbreviation for the French “manufacture d’horlogerie,” the term ‘manufacture’ refers to a watch company that designs, manufactures, and assembles all the components of a caliber.

Marine Chronometer
Specifically designed for navigation at sea, a marine chronometer is an accurate timepiece that allows for the calculation of longitude. Mechanical marine chronometers are gimbal mounted to retain the horizontal position necessary for their precision.

Mechanical Watch
Though there are many subtle variations, both types of mechanical watch, hand-wound and automatic, are powered by a mainspring and regulated by a balance.

Minute Repeater
Usually actuated by a slide or button, a minute repeater sounds hours, quarters, and minutes on demand using bells or a gong.

Cash for Used WatchesMoon Phase
A moon phase complication displays the phases of the moon. The moon phase is typically depicted by a rotating disc with two moons, visible through a half circle aperture. As the aperture obscures the part of the moon that is not lit, the correct lunar phase is revealed.

Motion Works
The motion works is the mechanism that gives motion to the hands of a mechanical watch, translating the action of the escapement into readable time. It also allows the manual setting of the watch’s hands without rotating the entire movement.

The movement is the complete assembly in a watch or clock that functions as the engine for keeping time and powering any other complications.

NATO Strap
Originally made for British military use, a NATO strap is simply a watch strap made of nylon. The first of these was issued 1973, and was made only in “Admiralty Grey” with a width of 20mm and a chrome plated brass buckle, though today they are available in many colors and sizes.

Observatory Chronometer
Highly accurate mechanical timepieces, observatory chronometers are chronometers that have been tested and certified by an official testing agency, like the COSC. Historically, the most precise timepieces were entered into competitions administered by the astronomical observatories of western Europe, where they were held to the highest accuracy standards for 30 to 50 days.

Oscillation is the regular back and forth movement of of any object. In mechanical movements, it is the balance wheel or a pendulum that moves regularly between two extremes, allowing the keeping of time.

Pallet Fork
A part of a mechanical watch’s escapement, the pallet fork releases the escape wheel one tooth at a time each time the balance wheel swings. It also gives energy to the balance wheel to keep it oscillating.

Perpetual Calendar
A perpetual calendar is a complication that indicates the date, and automatically adjusts for the varying length of the month, including adjusting for leap year.

Power Reserve
As the mainspring uncoils on a mechanical watch, the amount of time it can run diminishes. The power reserve is the remaining amount of time a watch can run, and can be indicated on the dial’s face, much like a car’s fuel gauge.

A pulsimeter simply a scale on a watch used to measure pulse rate.

Quartz Movement
A quartz movement is based on the fact that when electrical current passes through a quartz crystal, it vibrates at 32,768 times per second. Electricity is provided by a battery, and carried to the crystal via integrated circuit. A stepping motor sends every 32,768th to the dial train, advancing the hands on the timepiece. Simple, accurate, and inexpensive, quartz movements revolutionized the watch industry in the 1970s, and now account for about ninety percent of the total market.

The Parts of a WatchRatchet Wheel
When winding a watch, it is the ratchet wheel that turns to coil the mainspring. The ratchet wheel is attached to the barrel’s arbor, and its pawl, known as a click, keeps it in place, ensuring that the mainspring does not unwind.

Usually expressed in +/- seconds per day, the rate is a measurement of how accurate a watch or clock is running. For each movement there is an acceptable range of variation in rate, as well as a maximum deviation.

Also called a “split-seconds chronograph” a rattrapante features two seconds hands for timing multiple simultaneous events or a series of events, like laps in a race. The “rattrapante” hand is either directly above or below the main chronograph hand, and can be started and returned to zero with the main hand. In addition, the rattrapante hand can also be repeatedly stopped and then returned to position with the main chronograph hand by means of a separate push piece.

A repeater complication sounds the time on demand, using bells or gongs. Usually actuated by a slide on the edge of the case, quarter repeaters indicate the time to the quarter hour, and minute repeaters indicate the time to the minute. Through a complex mechanism with its own small mainspring and gear train, tiny hammers strike gongs to indicate the time.

Retrograde Display
Unlike a traditional circular display, a retrograde display is one in which a hand travels through an arc to indicate the time or date, and when it reaches the end of the arc it snaps back to its original position.

Rotating Bezel
A rotating bezel is the ring surrounding the watch face that can be turned to perform a variety of tasks, from interval timing to mathematical and navigational functions.

On an automatic watch, the rotor is an eccentric weight that is caused to spin by the motion of the wearer. The rotor then winds the movement’s mainspring.

Sapphire Crystal
In watchmaking, a sapphire crystal refers to the cover that protects the watch face. Transparent, scratch-resistant, and shatter-resistant, sapphire crystals are synthetically made corundum, exactly like naturally occurring sapphire but without the impurities that result in color.

Screw-Down Crown
Screw-down crowns are threaded on the stem to actually screw down into the case, preventing any inadvertent adjustment or damage to the crown. On waterproof watches, the screw-down crown is often fitted with an o ring for a more watertight seal.

Self-Compensating Hairspring
First marketed under the name “Nivarox” in 1933, these hairsprings are made of an alloy that compensates for temperature variations that made traditional hairsprings less accurate. Within a few years of their introduction, self-compensating hairsprings made bimetallic balances, which had previously addressed temperature variation error, obsolete.

Shock Resistance
A shock resistant watch is certified to be able to withstand an impact equal to that of being dropped from a height of three feet onto a wooden floor.

Side-shake refers to the amount of horizontal play a pivot has in its jewel hole. Without a minimal amount of side-shake, the gears may not turn easily, but too much sideshake can cause the gears to bind, stopping the watch. Excessive side-shake can result from poorly lubricated jewels, and lead to worn pivots.

Online Watch GlossarySkeletonized Movement
A skeletonized movement features plates, bridges, barrels, and gear trains that have had all non-essential metal trimmed away, leaving only the ‘skeleton’ of the movement needed for full functionality. These movements are contained in so-called “skeleton watches,” which showcase the inner workings of the movement with cut away dials and transparent casebacks.


The completes our online watch glossary and dictionary of parts. If you have a luxury Swiss timepiece or valuable antique watch that you would like to sell for a fair cash offer, please contact Diamond Estate Jewelry Buyers for a free appraisal.

A watch caseback that “pops” or snaps into place is called a snap-back.

Stainless Steel
Stainless steel is a highly corrosion and rust resistant alloy of steel and chromium. Extremely strong and able to take a high polish, stainless steel is often used for watch cases and casebacks.

Stepping Motor
Found in quartz movements, a stepping motor moves the gear train, which then moves the hands of the watch.

Sterling Silver
Sterling silver is an alloy that is 92.5% silver and 7.5% copper, and is often used in watches and watch dials.

Straight Graining
Straight graining is a method of finishing a watch part, often bridges and springs, by rubbing an abrasive across the metal in one direction only.

Serving the same function as a bracelet or band, a strap is made of nonmetal material, such as rubber, leather, or cloth.

Subsidiary Dial
Also known as a subdial, a subsidiary dial is a small dial located somewhere on the main dial that indicates additional information from a complication, such as the date, or elapsed minutes on a chronograph watch.

Swiss Made
In order to be labeled “Swiss Made,” Swiss law dictates that 50% of the watch’s movement, as determined by the value of the components, must be made in Switzerland. Both the movement and the watch itself must also be assembled and inspected in Switzerland.

Tank Watch
Inspired by the Renault tanks used in World War I, the original tank watch was designed by Louis Cartier in 1917 and presented to General Pershing. The rectangular design with seamlessly integrated strap has become one of the most iconic and copied watches of all time.

Commonly found on chronographs, a tachymeter is a numerical scale on the bezel or dial that can be used to determine speed over a pre-measured distance.

A telemeter is a scale found on a watch dial that allows the calculation of distance based on time.

Tempering is the reheating and cooling of metal to improve its hardness. Steel is often tempered in watchmaking, and a byproduct of this process is a layer of oxidation, which produces the blue color seen in many watch screws.

Third Wheel
The third wheel is the part of a watch’s movement that sits between the center wheel and the fourth wheel. The third wheel functions to increase the gear ratio from the center to the fourth wheel.

Thirty Minute Register
A 30 minute register (or recorder) is a subdial on a chronograph that times intervals up to 30 minutes.

From the French word meaning “cask,” a tonneau watch resembles a cask or barrel in profile, with slightly bulging sides.

Named for the French word for “whirlwind,” a tourbillon is a cage that surrounds the balance wheel, balance spring, and escapement. Rotating constantly around its own axis while the balance wheel oscillates, the tourbillon was designed to eliminate positional error, or timing error resulting from the watch remaining in one position for an extended period.

Designed by Abraham-Louis Breguet in 1795 for use in pocket watches, the usefulness of a tourbillon in a wristwatch is debatable, as wristwatches tend to move constantly. Today, the tourbillon remains popular in many expensive mechanical wristwatches as a visually stunning testament to a watchmaker’s virtuosity.

Triple Date
A triple date watch features a calendar that displays the day, date, and month.

Tritium is a radioactive isotope of hydrogen that was painted on watch hands and indices to make them glow in the dark. Despite a consensus among scientists that it presented no health hazard, tritium paint was abandoned in favor of tritium gas filled tubes which now fulfill the same function.

In watchmaking, turning refers to the process of cutting metal with a lathe. The lathe rotates the workpiece, allowing the craftsman to apply the cutting tool to the turning piece.

UTC is the acronym for Universal Coordinated Time, and is often erroneously equated with Greenwich Mean Time (GMT). Though the two are based on the prime meridian that runs through Greenwich England, GMT is a time zone, and UTC is a time standard used as the basis for civil time and time zones throughout the world. Though neither GMT or UTC ever change for Daylight Saving Time, some countries switch to different time zones during their DST period.

One vibration in a mechanical watch is a single swing, in one direction, of the balance wheel—two swings is called an oscillation. The frequency of a watch movement is sometimes expressed in Hertz (Hz), which is oscillations per second, or in vibrations per hour, (vph). A common frequency is 4 Hz, which equals 28,800 vph. A chronograph with a 28,800 vph can time an event to the nearest 1/8th of a second, as it ticks 8 times per second.

Water Resistance
Any watch labeled simply “water resistant” is only able to handle minimal moisture like light rain or an occasional splash, and should never be submerged. Submersible watches will be labeled, though the number listed is NOT an indication how deep a watch can go underwater, but rather how much water pressure the case can withstand. Professional dive watches will have a rating of 200 meters or greater, as well as a specific ISO rating indicating their reliability underwater.

The gear train is made up of wheels and pinions, with large gears, called wheels, normally made of brass, and small gears, or pinions, usually made of steel. When the two are riveted together, the combined piece is still called a wheel.

Winding Stem
The winding stem is the mechanism used to wind and set the movement of a mechanical watch. By either pulling or pushing and then turning the crown at its end, the winding stem winds the mainspring and adjusts the different functions of the watch, depending on its position.

A world timer is a watch with a complication that displays the current time in major cities in all 24 time zones in the world.

Yacht Timer
Also called a regatta timer, a yacht timer is a countdown timer complication designed specifically for yacht racing. These specialized chronographs allow the yacht skipper to synchronize his watch with the official race clock, and the countdown can be displayed in various ways, including multi-colored rotating disks, colored dots, separate chronograph hands, and chimes at certain times during the countdown.

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