In 1986, Patek Philippe replaced the long-lived ref. 2499 perpetual calendar chronograph with the new ref. 3970, featuring the caliber CH27-70Q, based on a heavily modified Lemania 2310, succeeding the Valjoux-based caliber used in the ref. 2499. While adopting a similar dial layout to its predecessor, the reference 3970 features a smaller case dimension at 36mm diameter. The reference was produced in all four metals including yellow gold, pink gold, white gold and platinum across a total of four series spanning over 19 years. It is estimated that throughout its course of production, over 4,000 examples of the reference were produced.

The present example in yellow gold is part of the third series and is offered in attractive condition. It is believed that approximately 1,350 examples of third series 3970s across all metals were produced between 1989 and 1995, featuring a solid screw back case. The hallmarks stamped on the sides of the two lugs remain crisp and deep. The present ref. 3970EJ is considered a fantastic value proposition and will certainly impress collectors seeking a timeless and important Patek Philippe perpetual calendar chronograph wristwatch.