Audemars Piguet Royal Oak 15500ST.OO.1220ST.03

The case measures 41mm across and 10.4mm thick. Case material: Steel. Case size alone is a poor guide to how a watch wears; lug-to-lug length and how the bracelet drops off the case matter more, which is why we suggest trying one on before you commit.

Automatic, AP Cal. 4302. Power reserve is 70 hours. It beats at 28,800 vph. The movement uses 32 jewels.

It is rated to 50 meters, about 164 feet. That covers brief swimming. It is not a dive watch. One caution that applies to every watch on this page: a water resistance figure describes a new watch with fresh gaskets. On a piece that is years past its last service, treat the rating as unknown until it has been pressure tested.

Royal Oak Selfwinding. Collector nicknames are not official Audemars Piguet names, but they are what people actually search for and what they are called across a showroom.

Yes. We buy this reference outright, and we lend against it if you would rather keep it. We are a family-owned San Diego buyer established in 2006, our appraisers are GIA-trained, and the appraisal is complimentary with no obligation to sell. You can bring it to our Gaslamp showroom at 907 Sixth Ave or start online. If you are looking to buy this reference instead, tell us and we will let you know when one comes in.