The Patek Philippe reference 3970 was launched in 1986 and remained in production until 2004. It is a perpetual calendar chronograph in a round 36mm case, made in precious metals such as 18k yellow gold (3970EJ) and platinum (3970EP). The dial combines a two-register chronograph with a perpetual calendar: day and month in twin apertures below 12 o’clock, a running seconds and 24-hour indicator at 9 o’clock, a 30-minute counter at 3 o’clock, and a moon phase surrounded by the date at 6 o’clock. Power comes from the manually wound calibre CH 27-70 Q with 24 jewels. It matters because it carried the brand’s serially produced perpetual calendar chronograph from the long-running 2499 into the modern era.

The key change from the 2499 was the movement. Where the earlier reference relied on a Valjoux base, the 3970 used a heavily modified Lemania 2310 ébauche, finished by Patek Philippe to its own standards. The smaller 36mm case with stepped lugs kept the classical proportions of its predecessors. Over nearly two decades the model evolved through several series that collectors distinguish by details such as baton numerals, leaf (feuille) hands and solid or display case backs. The 3970 led on to the 5970 and to the in-house perpetual calendar chronographs that the brand makes today.

Collectors often describe the 3970 as the best value among Patek Philippe high complications, since it offers the same type of complication as a 2499, which can be worth well over 500,000 USD, at a fraction of the price. Demand has been rising and the model has become a trophy purchase for newer collectors. At Phillips Geneva, a yellow gold 3970E from about 1993 sold for CHF 63,000 against an estimate of CHF 45,000 to 65,000. The reference 3970 is no longer produced; the perpetual calendar chronograph continues in the current collection with references such as the 5270.