Audemars Piguet Royal-Oak Annual Calendar Blue Dial with AP service Invoice ref. 25920STWe have a real soft spot for Royal Oak models with added complications, and this superb example delivers with an annual calendaror, in Audemars Piguets own words, the Quantime Annuel. This specific reference was introduced in 1999 and discontinued just a few years later, making it a relatively short lived and increasingly collectible Royal Oak. The 36 mm stainless steel case is in exceptionally sharp condition, complete with the side correctors used