A serial number is the individual number a maker gives each watch, stamped or engraved on the movement and often on the case. Makers used them to keep their own records, usually in rising order. Looking one up can give a rough year of manufacture, though not an exact date.
Where is the serial number on a watch?
Every movement carries one, because makers numbered their watches to keep their own records. At Audemars Piguet, for example, the movement number is engraved on the baseplate or on one of the bridges. Cases are a different matter. Case makers delivered them without numbers. The watch company usually stamped its own serial into the case when it fitted the movement. Some cases show more than one long number. If so, one of them usually identifies the design or model of case, not the individual piece. On antique pocket watches, the number that matters for identification is the one on the movement, not the case.
Can a serial number date a watch?
Only roughly. Numbers were normally handed out in order, going up by one each time, so a maker could track production. Looking up a serial number gives a rough year of manufacture rather than an exact date. The American Watch Co., for one, started its numbering at 50 in 1852. Audemars Piguet also gives out movement numbers in increasing order, but its numbers do not show how many watches were made. The numbers stamped inside a case back are seldom much help with dating. Repairers also often swap movements. A watch may no longer hold its original movement, so its serial-based date may be wrong.
Not to be confused with
A model number names a type of watch, much as a first name names a person. A serial number, by contrast, identifies one single watch. Two watches of the same model share a model number, but each has its own serial. At Audemars Piguet, one number served for both case and movement. For about 75 years, the firm used the same number on a watch’s case as on its movement.
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