Short answer
No Audemars Piguet reference 16402 appears in AP's published model lists or in the auction archives we checked. Known Royal Oak references sit in other ranges: 5402 and 15202 for the 39 mm Jumbo, 14790 for the 36 mm model, 15500 for the 41 mm model. Listings that use 16402 are either mislabeled watches or replica listings that borrow a number. Treat the number as a warning sign, not as an identification.
Where 16402 turns up
- Marketplace posts with no caseback photo.
- Replica sites that rotate reference numbers to dodge takedowns.
- Second-hand ads that copy a number from another listing.
Checks that matter more than the number
Case size and thickness
Measure with calipers, not a ruler. A genuine 15202 Royal Oak measures 39 mm across and 8.1 mm thick. A watch sold as a 15202 case at 10 mm or more is not a 15202 case. Replica cases run thick because the movement inside is thicker than an in-house caliber.
Bezel screws
The Royal Oak bezel carries eight hexagonal screws. On genuine pieces the slot in each screw head sits at a consistent angle around the bezel. On many replicas the slots sit at random angles, and the screw heads stand above the bezel surface instead of sitting flush.
Dial
Check the tapisserie grid. Replica dials show shallow squares with rounded edges, a date font that sits low in the window, and an applied AP logo with a heavy or filled letterform. Genuine printing is sharp under a loupe at 10x.
Movement
Period-correct Royal Oaks use in-house calibers: 2121 in the Jumbo, 3120 in later 39 mm and 41 mm models, 4302 in the current 15500. Ask for a clear movement photo. Replica movements show plate edges with no beveling, rotor engraving in the wrong font, and a balance wheel that does not match the reference.
Caseback and paperwork
The caseback carries a reference number and a case number, both engraved. AP offers an Extract from the Archives that lists the reference, case number, and original sale date. A seller who will not send the case number for an archive check is a seller to skip.
Price
Steel Royal Oak references in the 15202 and 15500 range sell in the tens of thousands of dollars. A complete watch offered at a few hundred dollars is not that watch, no matter which number is printed on the back.
Questions to ask a seller
- Send a photo of the caseback with the reference and case numbers legible.
- Send a movement photo.
- State the measured diameter and thickness.
- State the service history and any AP service papers.
- Allow a third-party inspection or a return window.
Limits of this guide
Photos hide detail. A watchmaker with the piece in hand, or AP's archive service, gives a firmer answer. We could not confirm that reference 16402 was ever produced. If AP confirms it in writing, that changes the answer above.