The present yellow gold example hails from the rarest and most desirable first series, and it is an extremely early and collectible example from 1986, being the fifth one made in the first series. The casemaker key number 28 stamped on the inside case back indicates that the yellow gold case was made by Ateliers Réunis. The gorgeous silver dial with the slightly darker sub-dials, sticker protected snap-on caseback, applied gold rectangular indexes and feuille hands further confirm it as a first series example.

First series (1986 – 1988) – Features a snap back case, feuille hands and rectangular indexes. Only produced in yellow gold with an estimated 100 examples produced, starting with the movement number 875’000 (The present example is the fifth first series example with the movement number 875’004).

Preserved in superb condition, the satin-brushed silver dial of the present specimen is beautifully preserved, and the case retains its strong stepped lugs stamped with legible hallmarks. It is offered with its certificate and presentation box, and is further delivered with a Patek Philippe Extract from the Archives, confirming its date of manufacture in 1986 and its subsequent date of sale on 3rd February 1987. This tremendously rare and collectible Patek Philippe reference 3970 will surely impress discerned collectors seeking for a timeless and important Patek Philippe perpetual calendar chronograph wristwatch.