According to the collector book on calendar watches published by Audemars Piguet the first reference of the Royal Oak perpetual calendar was the reference 25554 which was produced from 1983 to 1991 in steel, two-tone, yellow gold and platinum (made respectively in 49 examples in steel, 229 in yellow gold/two-tone and 1 in platinum). The second version (not counting the skeletonised version), like this watch was launched in 1982 and sold until approximately 1998 (272 pieces in steel, 422 in yellow gold, 72 two-tone, 1 in white gold and 33 in platinum), meaning that during its entire production of 15 years, only about 15 pieces a year were sold in stainless steel worldwide. Hardly recognisable from the first versions, only slightly thicker (0.75 mm in fact), one can notice these early examples by the lack of leap year indicator (according to Audemars Piguet these new versions were launched around 1993 with the new caliber 2120/2802). Complete with its original certificate and winding box, this example has been preserved in excellent overall condition.