Launched in 1986, the Patek Philippe ref. 3970 replaced arguably the most admired perpetual calendar chronograph wristwatches of all time, ref. 2499. As pioneers of the perpetual calendar chronograph wristwatch, Patek Philippe introduced the world’s very first, referenced 1518 in the early 1940’s. Marking an important era and milestone for the firm, perpetual calendar chronograph timepieces manufactured by Patek Philippe are the utmost importance and highly executed to perfection. Upgraded from its previous Valjoux based calibre, Patek Philippe introduced an entirely new Lemania based calibre CH 27-70 Q with two new features added, a leap year indicator and a 24-Hour hand.

The reference was produced for a total of 19 years and seized in 2004. During its production span, 4 series were produced alongside its rare sapphire cased counterpart ref. 3971. Examples from the 1st series featured a solid snap-on case back, 2nd series examples displayed baton indexes with Feuille hands with a waterproof screw down case back and referenced with an additional “E” which stands for “Etanche” meaning “waterproof”. It is believed that 400 examples in total were encased in yellow gold from the 2nd series. Examples from the 3rd series featured a merge between the ref. 3970 & 3971 offered with two case backs: sapphire and solid. The 4th series bears the same features as the 3rd series however with a deployant clasp instead of the traditionally used pin buckle.

The present example from the 2nd series manufactured in 1988 is confirmed by its baton indexes, Feuille hands, its movement number and case number matching the period. Furthermore, it features a solid screw-down case back with two hallmarks stamped and another two hallmarks stamped to the outside of the top left lug and bottom right lug.