With Patek Philippe presentation box, Certificate of Origin and product literature.
Reference 3941 is possibly the rarest variant of the 3940 family of automatic perpetual calendar wristwatches. Since the glazed backs were not numbered, Patek Philippe chose instead to apply the case number inside the upper case part, underneath the bezel.
Manufacture of references 3940 was launched in 1985 and continued production until approximately 2007. The model was originally produced with a snap on back, however due to customer demand, they later created the reference 3941 with a glazed snap on back and discontinued in 1990.
This model is illustrated in Patek Philippe Wristwatches by Martin Huber & Alan Banbery, second edition, pp. 292 & 293.