75. 75Y Patek Philippe. A fine 18K gold automatic perpetual calendar wristwatch with moon phase Patek Philippe. Belle montre bracelet en or jaune 18K (750) calendrier perpétuel et phase de lune mouvement automatique Reference: 3940 Date: Purchased 23rd December 1987 Movement: 27-jewel Cal.240Q automatic, adjusted to heat, cold, isochronism and 5 positions, stamped with the Seal of Geneva, Gyromax balance, 22K gold micro-rotor, No.770347 Dial: Silvered, applied 18K gold pointed baton hour markers, dot outer minute markers, subsidiary dials at 3, 6 and 9 indicating day combined with 24-hour display, month combined with leap year indication, and phases of the moon combined with date, gilt dagger hands Case: Brushed and polished round, solid snap on back, quick set buttons in the band at 6, 9 and 12, No.2831401 Strap/Bracelet: Black crocodile leather Buckle/Clasp: Signed 18K gold buckle Signed: Case, dial & movement Size: 36mm Weight: 59,34g Accompaniments: Patek Philippe box, outer card, quick set tool, Certificate of Origin In 1984 Patek Philippe launched the reference 3940, to replace the reference 3450. At the time, it was their slimmest automatic perpetual calendar. In the first year of production only 100 examples were manufactured but by 1985, the model went into standard production. It was discontinued in 2007, and replaced by the reference 5140.