Introduced in 1986 as the successor to the legendary ref. 2499, the ref. 3970 marked a significant transition by adopting a modified Lemania-based ébauche, departing from the previous Valjoux movement. While upholding the distinctive aesthetics reminiscent of both the references 1518 and 2499, the ref. 3970 introduced notable enhancements, including a leap year and 24-hour indication for the first time.

The reference was produced in yellow gold, pink gold, white gold and platinum across a total of four series with production spanning over 19 years. It is estimated that throughout its course of production, over 4,000 examples of the reference were produced. The 2nd series produced between 1987–1990, features a solid screw back case “E – Etanche”, feuille hands and baton indexes. Produced in all four case materials with an estimated 450 examples produced across all metals.

The present “fresh to the market” example is part of the 2nd series with screwed caseback from circa 1991, making it one of the very last examples from the series before the firm started to offer an extra sapphire caseback, marking the dawn of the third series. The hallmarks on both sides of the lugs are exceptionally crisp, making this a very well-preserved example. Accompanied by its Certificate of Origin and presentation box, the present ref. 3970E in platinum is a prized timepiece for collectors who appreciates the horological excellence of Patek Philippe that defined the perpetual calendar chronograph.