Where do I find the calibre number of a watch movement?

Most Swiss and many other movements carry the calibre number and the trademark of the movement maker on the main plate, often under the balance wheel or beneath the dial, rather than on the bridges where the brand's name is engraved. Opening a case should be left to a watchmaker, but display backs and auction photographs often show enough to read it.

What does the number of jewels tell me?

Jewels are synthetic rubies used as bearings where friction matters most. A simple hand-wound watch needs about 15 to 17; automatics and chronographs need more. A higher number is not by itself a sign of quality, and United States import duties made 17 jewels a common figure for movements sold there.

How do I tell a manual, automatic or quartz movement apart?

An automatic has a winding rotor across the back of the movement; a hand-wound movement shows its winding wheels and barrel without a rotor; a quartz movement shows a battery, a coil and a circuit, and its seconds hand usually jumps once a second.

Encyclopedia · Movements

Movement & calibre database

Technical records for landmark calibres — from railroad pocket watches to tuning-fork, quartz and Spring Drive movements. Select up to four to compare. For how the parts work, see the mechanism encyclopedia.

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Side-by-side comparison

Specification	Sellita SW200-1	ETA 2824-2
Manufacturer	Sellita	ETA (Swatch Group)
Type	Automatic	Automatic
Winding	Automatic (bidirectional rotor), hand-winding, hacking	Automatic (bidirectional rotor), hand-winding, hacking
Production	2000s–present	1971 (2824), 2824-2 revision later
Country	Switzerland	Switzerland
Diameter	25.6 mm (11½ lignes)	25.6 mm (11½ lignes)
Height	4.6 mm	4.6 mm
Jewels	26	25
Frequency	28,800 vph (4 Hz)	28,800 vph (4 Hz)
Power reserve	c. 38–41 h	c. 38 h (longer in later versions)
Complications	Date	Date
Status	Documented	Documented

Guide

How to identify the movement in your watch

The movement is the part of a watch that keeps time, and its calibre is the maker's name for one design of movement. Knowing the calibre tells you more about a watch than the name on the dial: it dates the watch to a production window, shows whether parts are still available, and reveals when a famous brand used a movement bought from a specialist maker.

1. Read the marks on the movement

Brands engrave their own name on the visible bridges, but the factory that made the raw movement (the ébauche) usually stamped its trademark and calibre number on the main plate — under the balance wheel, beside the winding wheels or beneath the dial. Swiss ébauche makers such as Valjoux, Landeron, A. Schild, Felsa, Peseux, Unitas and, later, ETA supplied hundreds of brands this way, so two watches with different names can share the same calibre. Opening a case is a job for a watchmaker, because a slip can scratch the movement or let in dust; for a first look, use a display back, a dealer's or auction house's movement photograph, or the service paperwork.

2. Recognise the type

Hand-wound: the winding wheels and mainspring barrel are visible, with no rotor across the back.
Automatic: a weighted rotor, a half-circle or a small inset rotor, winds the mainspring as the wrist moves. Early "bumper" automatics swing through part of a circle and bounce between springs.
Electric and tuning-fork: a battery with a balance driven by a coil, or a small tuning fork with a humming tone, from the late 1950s to the 1970s.
Quartz: a battery, a circuit and a stepping-motor coil; the seconds hand usually jumps once a second.

3. Count the jewels and listen to the beat

Jewels are synthetic rubies used as bearings where friction matters most. A simple hand-wound watch needs about 15 to 17; automatic winding, calendars and chronographs add more. A higher count is not in itself a sign of quality, and United States import duties charged extra for movements with more than 17 jewels, so 17 became a common figure for watches sold there. The beat rate, given in vibrations per hour, is another dating clue:

Typical beat rates and when they were used
Beat rate	Where you find it	Example
14,400–18,000 vph (2–2.5 Hz)	Pocket watches and most wristwatches until the 1960s	Hamilton 992 (18,000)
19,800–21,600 vph (2.75–3 Hz)	Many automatics and chronographs from the 1960s onwards	Seiko 6139 (21,600)
28,800 vph (4 Hz)	Standard for good mechanical calibres from the late 1960s to today	ETA 2824-2, Rolex 3135
36,000 vph (5 Hz)	High-beat calibres for finer timing	Zenith El Primero (1969)
360 Hz	Tuning-fork electronic watches	Bulova Accutron 214
8,192–32,768 Hz	Quartz watches: early models used various crystal frequencies before 32,768 Hz became the standard	Seiko 35A (Astron, 1969): 8,192 Hz

4. Measure the size

Swiss and French makers give movement sizes in lignes (one ligne is about 2.256 mm), so a 10½‴ calibre is about 23.7 mm across. The figure belongs to the movement, not the case, and helps match a calibre to a catalogue entry; the horology calculators convert lignes to millimetres.

What a calibre does not tell you

A calibre was often made for decades and fitted to many brands, so it gives a window rather than a year, and a movement may have been replaced during a repair. Check that the movement fits its case without spacers, that the dial feet line up with the plate, and that case and movement numbers agree with the maker's records where an archive exists.

Next steps

Common questions

Where do I find the calibre number of a watch movement?: Most Swiss and many other movements carry the calibre number and the trademark of the movement maker on the main plate, often under the balance wheel or beneath the dial, rather than on the bridges where the brand's name is engraved. Opening a case should be left to a watchmaker, but display backs and auction photographs often show enough to read it.
What does the number of jewels tell me?: Jewels are synthetic rubies used as bearings where friction matters most. A simple hand-wound watch needs about 15 to 17; automatics and chronographs need more. A higher number is not by itself a sign of quality, and United States import duties made 17 jewels a common figure for movements sold there.
How do I tell a manual, automatic or quartz movement apart?: An automatic has a winding rotor across the back of the movement; a hand-wound movement shows its winding wheels and barrel without a rotor; a quartz movement shows a battery, a coil and a circuit, and its seconds hand usually jumps once a second.