44. 44Y Audemars Piguet. A fine 18K gold automatic perpetual calendar wristwatch with moon phase Audemars Piguet. Belle montre bracelet en or jaune 18K (750) calendrier perpétuel et phase de lune mouvement automatique Model: Quantième Perpétuel Reference: 25548BA, No.2913 Date: Circa 1980 Movement: 38-jewel Cal.2120/2 automatic, adjusted to cold, isochronism and 5 positions, 21K gold rotor, No.286955 Dial: White, applied gilt baton hour markers, black outer minute divisions, subsidiary dials at 12, 3 and 9 for day, date and month, moon phase indication at 6, gilt pointed baton hand Case: Brushed and polished round, snap on back, stepped bezel, quick set buttons at 4, 8 and 10, No.C44663 Strap/Bracelet: Audemars Piguet black crocodile leather Buckle/Clasp: Signed 18K gold double folding clasp Signed: Case, dial & movement Size: 36mm Weight: 64,38g Accompaniments: Audemars Piguet watch winding box, outer card, Instructions booklet, quickset tool, box key Conceived in secret and launched in the midst of the quartz crisis, Audemars Piguet's 1978 release of the world's thinnest self winding perpetual calendar wristwatch was one of the greatest horological innovations of the late 1970s. Jacqueline Dimier, famed for her incredible contribution to the Royal Oak, was the design mastermind behind the original 5548 Perpetual Quantieme. The 5548 was her playground from which she went on to design a vast number of magnificent models and variations. The reference 5548 is famously the first wristwatch to be fitted with the ultra-thin calibre 2120/2800 and went on to become a huge success for the company, the most prolific perpetual calendar in its time for Audemars Piguet, selling at its peak 675 examples in a single year. The reference 5548 can be found across both B & early C series.