The Audemars Piguet reference 5516, introduced in 1955, is a perpetual calendar wristwatch and the first serially produced wristwatch model to display the leap year cycle. The example sold by Phillips in 2017 has a yellow gold case of 36.5 mm and a manually wound 13-ligne calibre 13VZSSQP with 18 jewels. The dial is two-tone, with sunken sub-dials finished with circular graining and raised champlevé enamel lettering, showing day, date, month, moon phase and the leap year. Until then, a leap year indication had only been found on perpetual calendar pocket watches, which makes the 5516 a key step in the history of the complication on the wrist.

Audemars Piguet had made calendar pocket watches since its founding in 1875, but it was Patek Philippe that made the first perpetual calendar wristwatch in 1925. According to the brand’s own research, three perpetual calendar wristwatches made around 1950 had no leap year display. The 5516 added it, and production was tiny: watchesbysjx counts 12 perpetual calendar wristwatches in total, nine of them with the leap year indicator, made until 1957. Phillips notes that the first three examples of the 5516 had the leap year at 6 o’clock with fully spelled months, while the later six moved the leap year sub-dial to 12 o’clock.

Collectors treat the 5516 as one of the most important vintage Audemars Piguet watches. Phillips points out that no other brand offered a perpetual calendar with leap year indication until Patek Philippe’s reference 3450 in 1981. At Phillips New York in October 2017, a 1957 example in yellow gold sold for USD 675,000, well above its estimate of USD 300,000 to 600,000. Writers praise the balance of the later two-tone dial, while the extreme rarity means few collectors will ever handle one. The reference 5516 is no longer produced; the perpetual calendar remains a core complication in the brand’s current collections, including the Royal Oak Perpetual Calendar.