The language
Watch glossary
Horological terminology, from basic components to the complications that make a movement difficult — each term linking to the calibers and watches it describes.
Annual Calendar
ComplicationA complication that automatically adjusts for months of different lengths, requiring manual correction only once a year (at the end of February). A perpetual calendar removes even that correction.
Automatic
MovementA mechanical watch that winds itself using a rotor powered by the wearer's wrist movement. Also known as a self-winding watch. It is the dominant construction here: 635 of the 1,004 catalogued calibers wind automatically, against 310 hand-wound and 59 quartz.
Balance Wheel
MovementThe oscillating wheel that governs a mechanical watch's rate, doing the job a pendulum does in a clock. It swings back and forth on its hairspring, and each swing lets the escapement release one step of the train. The rate is quoted in vibrations per hour: 28,800 vph, or 4 Hz, is the modern standard, used by the Rolex 3235 and the Breitling B01; Omega runs its co-axial calibers at 25,200 vph; Patek Philippe's 240 and most Audemars Piguet automatics beat at 21,600 vph, which draws less energy; and the Lemania-based CH 27-70 Q still runs at 18,000. A faster beat resists disturbance better; a slower one lets a small barrel run longer.
Bezel
CaseThe ring surrounding the crystal on the top of a watch case. Can be fixed, rotating, or bidirectional depending on the watch's function. A dive bezel turns one way only, so a knock can shorten the elapsed time it shows but never lengthen it.
Caliber
MovementThe specific movement used in a watch. Usually identified by a reference number (e.g., Rolex Caliber 3235, Omega Co-Axial 8900). Each one has its own page in the caliber directory, listing its specifications and every watch in the library that uses it.
Chronograph
ComplicationA watch complication that functions as a stopwatch. Typically includes sub-dials for elapsed seconds, minutes, and sometimes hours. The Valjoux 7750 is the workhorse of the genre, and appears in this library under many different maisons' names.
Co-Axial Escapement
MovementThe escapement designed by the English watchmaker George Daniels and put into production by Omega in 1999. A Swiss lever escapement transmits energy to the balance by a sliding action that needs lubrication and wears as the oil ages; the co-axial uses two wheels on one axis and delivers its impulse by a pushing action with almost no sliding friction, so it holds its rate longer between services. Omega first fitted it to an ETA 2892 base as the 2500, then designed the 8500 around it in 2007, and every Omega mechanical caliber since, including the Master Chronometer family and the Moonwatch's 3861, uses it. It runs at 25,200 vph in most Omega calibers, a beat chosen to suit the escapement rather than inherited from the base.
Column Wheel
MovementThe castellated wheel that controls a chronograph's start, stop and reset. Each press of the pusher turns it one step, and the chronograph's levers ride onto its teeth or drop into the gaps in a fixed sequence. It is machined and hand-adjusted, and it gives the pusher a short, even, precise click; the cheaper alternative is a stamped cam, which the Valjoux 7750 family uses and which travels further and lands softer under the finger. The column wheel was the classical construction, in the Lemania 2310-based movements of Patek Philippe and Omega, and it is the construction the in-house chronographs returned to: the Breitling B01, the Rolex 4130, the Omega 9300 and the Audemars Piguet 4401 all use one, paired with a vertical clutch.
Complication
ComplicationAny function on a watch beyond simple timekeeping. Examples include date, chronograph, moon phase, perpetual calendar, and tourbillon.
COSC
MovementThe Contrôle Officiel Suisse des Chronomètres, the Swiss institute that certifies chronometers. It tests a bare movement, not a cased watch, over fifteen days in five positions and at three temperatures, and passes it if the average daily rate stays between −4 and +6 seconds. A movement that passes may be called a chronometer, and only a small share of Swiss production is submitted. Breitling submits every movement it sells, mechanical or quartz, which is why even its SuperQuartz B71 is a chronometer. Rolex submits every movement and then tests the cased watch again to its own tighter Superlative Chronometer standard of two seconds a day. Omega's Master Chronometer begins with a COSC certificate and adds a second programme on top.
Crown
CaseThe knob on the side of a watch case used to set the time and date. On water-resistant watches, it often screws down to ensure a seal. It is also how a hand-wound movement is wound back up to its full power reserve.
Escapement
MovementThe mechanism that releases the movement's energy in equal, counted steps. It sits between the gear train and the balance wheel: an escape wheel tries to run forward under the mainspring's push, a pallet fork lets one tooth go each time the balance swings, and the tick you hear is that release. Almost every mechanical watch here uses the Swiss lever escapement, a design settled in the nineteenth century. The exception is Omega's co-axial escapement, which reduces the sliding friction of the lever and runs in the 2500 and every Omega caliber since. Rolex's Chronergy, introduced with the 3255 in 2015, is a lever escapement made thinner and more efficient rather than a new type.
Flyback
ComplicationA chronograph function that resets and restarts the timing on a single press while the chronograph is running, where a standard chronograph needs three: stop, reset, start. It was designed for pilots timing successive legs of a course, and it demands more of the mechanism, because the reset hammers must act on a train that is still coupled. The Audemars Piguet 4401, the IWC 89361 and Panerai's P.9100 are the flyback movements with the most watches here, and the Rolex 4130 is a well-known example of a chronograph that is not one. It is distinct from the rattrapante, which adds a second hand rather than a shortcut.
GMT
ComplicationA second time zone shown on the same dial, most often by an additional hour hand that turns once in 24 hours and reads against a 24-hour scale on the bezel or the dial's edge. The name comes from Greenwich Mean Time, the reference the original Rolex GMT-Master of 1955 was built to show for Pan Am crews. The useful distinction is which hand adjusts: on a "true" GMT the local hour hand jumps in one-hour steps from the crown so that a traveller resets it on landing, while on the simpler "caller" type the 24-hour hand is the one that moves. The Rolex 9002 and the Breitling B04 are the first kind; the Breitling Caliber 32 is the second. Panerai fits it to more of its range than most, with 57 GMT references in the Radiomir alone.
Grand Complication
ComplicationA watch that combines multiple complex complications — typically a minute repeater, perpetual calendar, and chronograph — in a single timepiece.
Hacking Seconds
MovementA stop-seconds function: pulling the crown to the setting position halts the balance wheel, so the seconds hand stands still and the watch can be set to a reference signal exactly. It began as a military requirement, for synchronising watches before an operation, and is now standard on most movements, though not all. The ETA 2824 behind the Breitling Caliber 17 hacks, as does every current Rolex caliber, and Omega added hacking to the Moonwatch only with the 3861 in 2019, after fifty years of the 861 and 1861 running without it. Many older hand-wound movements, including the Unitas 6497 family, were built without it.
Hairspring
MovementThe fine spiral spring that returns the balance wheel to centre after each swing, and the part that decides how well a watch keeps time. A conventional hairspring is a steel alloy, which magnetism can disturb and temperature can soften. The modern answers are new materials. Rolex's Parachrom, a niobium-zirconium alloy, has been in its larger movements since 2000; its silicon Syloxi spring debuted in the 2236 in 2014. Omega's Si14 silicon spring has been in the 8500 family since 2011 and is the reason a Master Chronometer can be certified at 15,000 gauss. A Breguet overcoil, where the outer turn is raised over the spiral, is the traditional way to make the spring breathe concentrically, and appears in several of IWC's seven-day calibers.
Helium Escape Valve
CaseA one-way valve in the case of a saturation-diving watch that lets helium out. Divers who live in a pressurised habitat breathe a helium mix, and helium atoms are small enough to seep into a watch case over days; on decompression they expand faster than the case seals can release them and can blow the crystal off. The valve, developed by Rolex and Doxa in the 1960s, vents the gas safely. It is only needed by saturation divers, but it became a mark of a professional dive watch: the Omega Seamaster Diver 300M carries a manual one at 10 o'clock, the Planet Ocean the same, and the Rolex Sea-Dweller an automatic one at 9 o'clock. The Submariner, rated to 300 m, has none, because it was never a saturation watch.
Jewel
MovementA synthetic ruby set where a steel pivot turns, so that the pivot runs on a hard, smooth surface that holds oil and does not wear. The jewel count on a spec sheet is a count of those bearings, and it maps how much mechanism a movement contains rather than how good it is. A hand-wound time-only movement needs about 17, as the Unitas-based Panerai OP II records; an automatic three-hander sits in the low 30s, the Rolex 3135 at 31; a column-wheel chronograph climbs to the 40s and 50s, the Breitling B01 at 47 and the Omega 9300 at 54; and a modular chronograph counts both its base and its module, which is why the Audemars Piguet 3126/3840 records 59. In this library the counts run from 3 to 117.
Lug-to-Lug
CaseThe distance from the tip of one lug to the tip of the other, measured vertically. Determines how a watch sits on the wrist. It is often a better guide to fit than case diameter, which is why it sits beside diameter and thickness on every watch page in the catalogue.
Luminescence
DialA coating applied to hands and indices to allow reading in dark conditions. Modern watches use Super-LumiNova or Chromalight. It replaced tritium, which glowed without being charged by light but decayed over time.
Mainspring
MovementThe coiled ribbon of steel that stores a mechanical watch's energy, wound by the crown or by the rotor of an automatic and housed in a drum called the barrel. Its length and the movement's appetite set the power reserve. A spring does not deliver power evenly: it pushes hardest fully wound and weakest near the end, which is why some makers stop the movement before the barrel is truly empty, and why a second barrel is the usual way to a longer reserve. Omega's 8500 and Panerai's P.9010 use two; IWC's seven-day 51111 uses one very large one; Panerai's P.2003 uses three for ten days.
Manufacture
MovementA watch brand that designs and produces its own movements in-house, rather than sourcing them from external suppliers. The alternative is an ébauche bought in and finished under the maison's own name — the ETA 2892 and the Unitas 6497 both appear in this library under several different caliber designations.
Master Chronometer
MovementOmega's certification since 2015, issued by METAS, the Swiss Federal Institute of Metrology, for the cased watch rather than the bare movement. A Master Chronometer must first be a COSC chronometer; the watch is then tested against eight criteria, including running correctly while exposed to a magnetic field of 15,000 gauss, a rate of 0 to +5 seconds a day measured over four days in six positions, and a power reserve and water resistance that match the claim. Every watch is tested, not a sample. The 8900 of the 2015 Globemaster was the first; the 8800, 8700, the 9900 chronograph and the Moonwatch's 3861 followed, and 694 watches in this library carry the certificate.
Micro-Rotor
MovementA small winding rotor set into the plane of an automatic movement rather than turning above it, so that the movement stays as thin as a hand-wound one. It is usually made of a heavy metal, gold or platinum, to recover the mass it loses in size. Patek Philippe's 240, introduced in 1977 with a 22-carat gold micro-rotor recessed into the mainplate, is the reference example and is 2.53 mm thick; its world-time version, the 240 HU, shows the type's advantage, since even the extra module keeps the movement under 4 mm. The trade is winding efficiency: a small rotor gathers less energy, which is why the 240 runs a slower 21,600 vph balance that asks less of it.
Moon Phase
ComplicationA complication that displays the current phase of the moon through an aperture on the dial. A well-cut moon phase gear drifts by only about a day per century, which is why it is counted among the more demanding complications.
Perpetual Calendar
ComplicationA complication that automatically accounts for months of varying lengths and leap years, requiring no date adjustment for decades or centuries. The simpler annual calendar handles month lengths but still needs correcting each February.
Power Reserve
MovementThe length of time a fully wound mechanical watch can run before stopping. Displayed as hours (e.g., 70-hour power reserve). The range in this library is wide: the Rolex 3235 holds 70 hours, while the Panerai P.2003 holds 240 — ten days.
Rattrapante
ComplicationA split-seconds chronograph: two chronograph seconds hands run together, a third pusher stops one of them to read an intermediate time while the other continues, and a second press sends the stopped hand flying to catch up. The name is French for "catching up". It is the most demanding of the chronograph complications, because the two hands must separate and rejoin without disturbing the running one, and it is correspondingly rare: IWC's Richard Habring built the first affordable one on a Valjoux 7750 as the 79230 in 1992, Breitling's B03 adds it to the B01, Omega's 3612 to the 3313, and Patek Philippe's CHR 27-70 Q combines it with a perpetual calendar in the ref 5004.
Rolesor
CaseRolex's name, registered in 1933, for a watch that combines steel and gold: a steel case and bracelet with a gold bezel, crown and bracelet centre links. It is not a plating; the gold parts are solid. Yellow Rolesor pairs steel with yellow gold, Everose Rolesor with Rolex's pink gold alloy, and white Rolesor is the quiet version, steel with only the fluted bezel in white gold. It is the natural state of the Datejust: of the 2,184 Datejusts in this library, 1,232 are Rolesor and only 116 are plain steel, and in the Datejust 36 the white Rolesor 116234 is the single largest family. The word appears in Rolex's own model names, which is why it is worth knowing when reading a reference number.
Tourbillon
ComplicationA rotating cage that holds the balance wheel and escapement, designed to counteract the effects of gravity on timekeeping accuracy. It was patented by Breguet in 1801 for pocket watches, which sit in one position; its practical value in a wristwatch, which does not, is debated. It stays uncommon: 531 of the 17,435 watches in this catalogue carry one in the model name — see what rarity means here.
Tritium
DialA radioactive isotope formerly used in luminous watch dials. Replaced by safer alternatives like Super-LumiNova since the late 1990s. Dials predating the change are marked T SWISS T or T<25 below six o'clock — see luminescence.
Vertical Clutch
MovementThe coupling that connects a chronograph to the running movement by pressing two friction discs together on one axis, rather than swinging a toothed wheel sideways into mesh. Because no teeth have to align, the chronograph seconds hand starts cleanly from a standstill instead of stuttering, and the chronograph can be left running indefinitely without disturbing the watch's rate. The cost is height: the clutch sits in the middle of the movement rather than on top. Rolex built the 4130 around one in 2000, and the Breitling B01, the Omega 9300, the Audemars Piguet 4401 and the Frédéric Piguet-based 2385 and Omega 3313 follow. Paired with a column wheel, it is now the majority architecture in this library.
Ébauche
MovementA movement supplied unfinished, as a set of plates, bridges and train, to be completed, decorated, regulated and cased by the buyer. For most of the twentieth century the Swiss industry ran on ébauches from specialist houses, and much of what a maison sold was its finishing of someone else's base. Lemania supplied the 2310 that Patek Philippe and Omega both built on; ETA's 2892 and Valjoux 7750 sit under Breitling, IWC, Omega and Panerai calibers here; Frédéric Piguet's 1185 sits under the Audemars Piguet 2385. The shift to in-house movements since the 2000s is largely a shift away from ébauches, and the manufacture label describes a maison that no longer buys them.