1. Audemars Piguet Ref. 5516
Perpetual calendars are an integral part of Audemars Piguet’s DNA and reference 5516 was the first perpetual calendar wristwatch to feature a leap year indicator on the dial. Only nine examples were produced, and only six of them have the leap year indication at 12 o’clock (four of them sit in the company’s Heritage Collection). This is a rare opportunity for collectors to own one of the most important watches in the history of watchmaking.