Audemars Piguet serial number checker, read from AP's own table

The number to look for is the large case number, engraved on the caseback. On an open caseback it is on the flat ring around the crystal, and on a solid one it is engraved across the back, usually as one letter and up to five digits, such as F59863. On a Royal Oak 5402 from the 1970s it is inside the case, and the number on the outside is the small number. Audemars Piguet calls these the big case number and the small Royal Oak number.

They are two different numbers. Since 1951 Audemars Piguet has numbered its cases separately from its movements. The case number is on the caseback or inside the case. The movement number is on the movement itself, on the baseplate or a bridge, and on a solid caseback it can only be seen with the case open. AP's own records hold both, and its Extract from the Archives confirms that the pair appears there. The case number is the better guide to when a watch was sold, because AP notes that a movement could be numbered years before it was finished and cased.

Each letter is a series. The first case numbers, from 1951, had no letter and ran from 101 to 105393. Around 1975 AP started again at B1 and moved to the next letter each time a series reached 99999: B, C, D, E, F, G, H, I, J and finally K. AP's table gives each one a window, B 1975 to 1990, F 2003 to 2010, J 2015 to 2020, and the windows overlap because cases were sold over several years.

A case number with no letter is either from before about 1976, when the run of plain numbers reached 105393, or it is a different number, such as a Royal Oak small number or the movement number. A case number made of random letters and digits, such as two letters, four digits and a letter, is from 2017 or later. AP moved to random numbers to make them harder to copy, and they carry no date.

It is a production number for the owner, engraved on the outside of a Royal Oak caseback, often after N°. The first Royal Oak, the 5402ST, used series A to D, such as A427 or C1709. From 1976 each new Royal Oak model counted its pieces from 1, with no letter, until the small number disappeared in the second half of the 2010s. A small number counts pieces of one model, so it does not date the watch by itself. A small B, C or D number shares its letter with the large case numbers, which is why the checker may show both readings.

Left to right. In 15500ST.OO.1220ST.01, 15500 is the model, ST the case material, steel, OO the standard finish with no gem setting, 1220ST the steel bracelet and 01 the dial version for that model. The reference names the model, not your watch, and it carries no date. AP says it is not engraved on the watch, so you will find it on the warranty card, the box and the papers.

Yes, and there are two documents, so ask for the right one. The Extract from the Archives, also called the Extrait de Registre, only certifies that the case and movement numbers appear in AP's records, and AP says it does not authenticate the watch. The Certificate of Authenticity is issued only by the Manufacture in Le Brassus after the watch is examined there, and it contains information about the watch and actual pictures. Both are arranged through an AP boutique, service center or authorized retailer. AP publishes no price for either.

No. Counterfeits carry case numbers too, often copied from real watches in listings, so a number that fits AP's table proves only that it fits. A number that does not decode is not proof of a fake either. The finishing of the case, the dial and the movement carry far more weight, and only an examination of the watch can settle it.

Because that is how AP's own table is built. Each letter series ran for several years, and the series overlap: F runs 2003 to 2010 and G 2009 to 2015. AP calls the table an approximate dating and says only a full appraisal of the watch can confirm it. Dated auction lots fit the windows, for example F59863 cataloged circa 2006 and J11851 circa 2016.