Patek Philippe’s reference 3970 was a new generation of the brand’s famed serialised perpetual calendar chronograph first released in 1941 with the reference 1518, and followed ten years later by the reference 2499. Launched in 1986, the new reference featured a similar aesthetic to its predecessors with pump-style pushers and down turned stepped lugs, however, the case diameter was reduced in size from 37.5mm to 36mm. The wristwatch was upgraded with a heavily modified Lemania 2310 base caliber, CH 27-70 Q, replacing the former Valjoux movement. Additionally, the dial was redesigned to include both leap year and 24-hour indications.

Beginning with serial number 875’000, the first 100 examples featured a snap on case back with applied gold sword indexes and feuille hands. The second series featured a screw-down, solid caseback, with the hallmarks stamped on the outside of the lugs. The third series featured a sapphire display back along with a screw-down solid caseback, like the present example. The fourth series is identical to the 3rd series.

The present example in platinum has a black dial with diamond indexes and assigned the reference 3970E (“E” – étanche meaning waterproof). Offered for the first time at public auction, the present model from 1994 is in excellent overall condition with strong case proportions and a vibrant black lacquer dial. The watch is accompanied by its original Certificate of Origin, presentation box, hang tag and ever so important, additional solid case back.