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Watch Glossary

Kseniya Burns


12- Hour Register:  Also known as a register.  A sub-dial that can record time in 12 hour intervals.

24- Hour Recorder:  Also known as a register.  A sub-dial that can record time in 24 hour intervals.

30 Minute Recorder:  Also known as a register.  A sub-dial that can record time in 30 minute intervals.


Acrylic Crystal: A plastic crystal used in the vintage and early model Rolex watches before the introduction of a synthetic sapphire crystal.

Aperture: An opening on the dial of the watch that displays day, date, or hour.

Analog: refers to the watch that uses watch hands to display the time.

Altimeter:   A  complication that measure altitude.

Annual Calendar:   Is one of the more complicated and thought after  watch movements. This complication shows day, date, month, and year.

Auto Rotor: Patented on January 14, 1932, Auto Rotor is the first self winding perpetual movement by Rolex.

Automatic Winding Movement: Also known as Self Winding Movement is a watch that has a rotor that responds to  the motion of the wearers wrist and winds the watch's mainspring rather than through turning the winding stem. If the watch is not worn for a period of about 48 hours or more, the watch will need to be wound manually.


Baguette: Thin rectangular or oval shape. Generally refers to a gemstone cut.

Bakelite:  A transparent acrylic material used on the bezel of a 1954 GMT-Master.

Balance: is an oscillator that regulates the speed of the movement of the watch.

Balance Spring: A hairspring that controls the swing of the balance.

Balance Wheel:  a part of the escapement .  Divides time into equal sections.

Bark Finish:  A finish on Rolex bracelets, some aftermarket bezels, and watch cases that resembles the pattern of tree bark.

Barrel: also known as the "Mainspring Barrel".  A box that holds the mainspring.

Beat:  Refers to the number of times per second or hour  that the balance wheel  completes a full arc of motion. Most Rolex models have ,  28, 800 Beats Per Hour or BPH.

Bezel:  A ring that surrounds the crystal of the watch.

Bi-Directional Rotating Bezel:  a bezel that can rotate clockwise and counter clockwise. Usually used in watches like Breitling Navitimer to perform mathematical calculation through the use of a slide-rule.

Boy's Size Watch:  see Mid-size

Brancard: refers to the shape of a Rolex Prince with flared ends.

Breathe:  refers to the expansion and contraction of the hairspring due to ambient conditions.

Brevet:  a French word that refers to a "patent" or a "certificate".

Bridge:  a movement plate.

Bubbleback:  a term used to describe early Rolex Perpetual models due to their thick case size that resembled a bubble.


Calendar Watch: a watch that displays a date, day and date, or day, date, and year.

Caliber:  the term used to describe the movement of a watch. Refers to the size, shape, and the style of said movement.

California Dial:  a split dial that features  Roman numerals on the top half and Arabic on the bottom half.

Case:   a container that houses the movement of a watch.

Center Sweep Seconds Hand: a seconds hand that is mounted on the center post of the dial.

Chronograph:  refers to a watch or another device with two independent functions. One features the time of the day and the other measures brief periods of time (a stopwatch). Various counters can be started and stopped independently of each other.

Chronometer:  For a Swiss watch to be called a Chronometer, a watch must undergo a series of rigorous tests at different temperatures and various pressure.

Cock:  a retaining device secured by a single screw.

COMEX:  a French diving company that helped Rolex develop the Sea Dweller based on an early Submariner model but with the addition of a helium escape valve to help with decompression.

Complications: refers to the additional watch functions such as a stop watch.

Concealed Clasp: a feature of a Rolex President bracelet where the foldover clasp is concealed underneath the bracelet links.

Co-Branded Watches:  a watch with two names: one of the manufacturer and one of the retailer.

COSC: stands for Controle Officiel Suisse Des Chronometres an official Swiss bureau that tests and certifies chronometers. Only those of the highest quality pass.

Countdown Timer:   a complication that allows the watch owner to calculate how much time has elapsed.

Crown:  a small button that appear on the side of the watch case that is attached to the winding stem. The crown is used to wind the watch and set the time and date.

Crown Guards:  a set of rails on the either side of the crown that protect it from damage.

Cyclops eye: refers to a glass bubble-like structure that is placed at the three o'clock position over the date window on Rolex watches. The magnification of the Cyclops eye lens is X2.5

Crystal:  the cover of a watch dial. A crystal can be made out of a synthetic sapphire, Plexiglas, Acrylic, or glass. Usually high end Swiss watches will feature a sapphire crystal. In some cases, some high end vintage watches will feature a Plexiglas or and Acrylic crystal.


Day Date:  A Rolex watch that features a day function at 12 o'clock and a date function at 3 o'clock. The Day Date is also known as the "President".

Deployment Buckle/ Clasp: a three folding enclosure that secures the two ends of the bracelet. Also known as the foldover clasp.

Dial: the "face" of the watch with indices, hands, and sub-dials.

Digital Watch: a watch that shows the time in numbers on a liquid crystal display (LCD) rather than through the use of hands and a dial.

Divers Extension:  an extension within the bracelet so the watch can fit over the wet suit. A common addition to the diver watch bracelets.

Double Quick Set:  a feature that allows the day and date to be set quickly through the use of a winding stem.


Ebauche: a "blank" movement. A movement without a mainspring or a balance.

Elapsed Time Rotating Bezel:  a gradually rotating bezel found in diving watches that tells the diver how much time has passed since the beginning of the dive.

End Piece: a hollow piece of metal that attaches the bracelet to the case.

ELT:  Emergency Locator Transmitter is a radio frequency beacon that is used in Breitling Emergency watch that allows rescue crews to locate and individual in distress. The ELT in the Breitling Emergency watch is similar to the ELT's that are found aboard civilian aircraft and boats and broadcasts on the civilian emergency frequency.

Escapement: a device that allows the power stored in the mainspring to be released through the gears to regulate time intervals.

Escape Wheel:  is the last gear in the lever escapement.


Flip Lock Clasp:   a clasp that features an extra lock to prevent accidental loss and is found on Rolex Oyster bracelets.

Flyback Chronograph:  a seconds hand on a watch that can be used to track time of multiple competitors in a race .


Gas Escape Valve: see Helium Escape Valve

Gauss: a measure of magnetic flux density.

Gear Train:  is a system of gears that transfers power from the mainspring to the escapement.

Gilt/ Guild:   see  Gold Plated

GMT:  or Greenwich Mean Time, Universal  Time Coordinate (UTC) or Zulu Time. A Universal time standard used by pilots and military to navigate through time zones.

Gold Plated: an application of a layer of gold over another metal.

Guilloche: or Engine Turning. An engraving technique where a very fine and precise pattern is etched or carved into the metal.


Hairspring:  also known as balance spring.  A spring that regulates timekeeping capacity of the watch by its tension.

Hacking:  a feature in some watches including Rolex where the seconds hand comes to a complete stop when the winding stem is pulled out to set the time.

Helium Escape Valve:   A feature developed by Rolex in conjunction with COMEX to help maintain the integrity of the watch while the diver undergoes decompression after a deep sea dive. Prior to the Helium Escape Valve being installed, a watch would lose its crystal or sustain other damage during decompression due to the rapid expansion of helium that was absorbed by the watch from the divers skin.

Hermetic:  a complete seal.

Horology:  a study of measuring time and instruments used to measure time.

Hunter Case:  a pocket watch case where the both side of the case (front and back) are protected with hinged covers.


Indices:  markers on the dial.

Integrated Bracelet:   a bracelet that is integrated into the case.


Jewels:  a precious stone that is used as a bearing at pivot points in a watch movement.

Jeweled Movement:  a movement that uses synthetic or naturally occurring precious stones at key pivot point to reduce friction.

Jubilee:  A Rolex bracelet style.


Lap Timer: a complication that allows the watch owner to time segments of a race or laps on the track.

Loupe:   a magnifying glass.

Lugs: an extension of the case by which the bracelet is attached to the case.

Luminescence:  a fluorescent coating that is used on hands, markers, and dials to allow the wearer to tell time in the dark.

Luminova:   an organic, non radioactive material used on luminous hands and markers in Rolex watches.


Mainspring: a coiled spring which provides the power to drive a mechanical watch movement.

Mechanical Movement: a movement based on the slow, incremental unwinding of the mainspring.

Mercedes Hands / Rolex Skeleton Hands:  a particular style of watch hands that resemble a Mercedes Benz symbol.

Micro-Stella:  the screws that adjust the balance.

Mid-Size:  describes any Rolex that is 20% smaller than the standard men's Rolex watch.

Milled Edge:  a specific edge that is found on the back of Rolex Oyster cases. Resembles a coin edge.

Mother-of-Pearl:  A thinly slice iridescent shell of a sea mollusk that is used to make watch dials.

Moon phase:  a complication that allows for accurate tracking of phases of the moon.

Movement:  is an integral part of the watch that allows the watch to keep time. An essential part of the watch.


Navigation Computer: see Slide-rule


Officially Certified Chronometer:  indicates that the watch bears the official chronometer rating.

Official Timekeeper: a designation that is given to a watch or a person that keeps track of elapsed time in specific events. Rolex is an official timekeeper for many of the European Golf tournaments, Yacht races, and Motor Sport events.

Oyster:  is a style of Rolex case and bracelet.


Power Reserve Indicator: a feature that shows when the watch needs to be wound.

Perpetual Movement:  a movement with a winding rotor that travels 360 degrees.

Precision: a term used by Rolex for all of their models that were not Officially Certified Chronometers.

President:  a Rolex bracelet style.

Push/ Push Piece:  a button on the watch that is used to work a specific complication.

Pins: see  Spring Bars


Quick Set:  a feature that allows for quick date setting via the winding stem.

Quartz Movement:  a battery powered movement that keeps time through the use of a crystal.


Radium:  the radioactive material used as the primary component of luminous markers in some vintage Rolex models pre 1950's.

Reference Number:  a unique number that identifies a watch.

Register(s):  refers to extra watch functions found in Rolex watches such as Rolex Daytona.

Rolesium:  a Rolex term used to describe a combination of Platinum and Stainless Steel.

Rolesor:  a Rolex term used to describe a combination of Stainless Steel and Gold.

Rotating Bezel:  is a ring that surrounds the dial of the watch that can be turned to perform a specific function. Most common on tool and sport watches.

Rotor: A part of an automatic (self-winding) movement that winds the mainspring.


Sapphire Crystal:  a lab grown crystal that is used to protect the dial. Sapphire crystal is colorless and extremely durable.

Shock Absorber:  a bearing that absorbs shock and protects crucial pivot points from damage.

Skeleton Case:  a watch case that is made out of a transparent material that allows the wearer to see the inner workings of the movement.

Slide-rule:  a device on the outer edge of the watch face and dial that consists of logarithmic or other scale allowing the wearer to perform complex mathematical calculations.

Stepping Motor:  a part of the quartz movement that moves the gear train. The gear train moves the hands of the watch.

Stop watch:  a watch with a seconds hand that measures intervals of time.

Sub-dial:  also known as the  subsidiary dial  a smaller dial that is positioned on the main dial and that keeps track of other functions such as elapsed time.

Subsidiary Seconds:   refers to the seconds subdial at 6 o'clock.

Super Balance:  a Rolex term used for the balance wheel of an auto rotor perpetual movement.

Sweeping Movement:   a feature of Rolex watches where the seconds hand "ticks" 6-8 times a second giving it the illusion of a sweeping motion.

Swiss A.O.S.C. :  or a certificate of origin. A certificate that identifies the timepiece as a device that was assembled in Switzerland with genuine Swiss parts.


Tachymeter:  a feature that measures speed  over predefined distance.

Tank Watch: a style of the watch that was inspired by World War I tanks and designed by Cartier.

Telemeter:   a feature that determines the distance of an object by measuring how long it takes sound to travel the distance.

Triplelock Crown:  a screw down crown that protects a Rolex watch movement from dust, water, and debris.

Tritium: a radioactive material used in luminous hands and markers of some vintage Rolex models.

Twinlock:  a screw down crown that features a dual seal against dust and water.

Two-tone:  see  Rolesor


Unidirectional Rotating Bezel:  a bezel that keeps track of elapsed time. Usually found on divers watches.


Water Resistant:   describes a level at which the watch is safe from water damage. Water resistance is usually measured in feet or meters and can be found in your watch manual.

Winding Stem:   a device that winds the mainspring.