Perpetual Calendar Chronograph 3970

In Context

At 36 mm it is classically proportioned: the size a dress watch was understood to be for most of the twentieth century, and small enough to sit under a cuff. The case back is open, so the movement is visible without taking the watch apart, and the sapphire crystal will resist everything short of deliberate abuse.

The movement is hand-wound, so winding it becomes part of the day rather than something the watch does for you. 60 hours of reserve is enough to set it down on Friday evening and find it still running on Monday. At 18,000 vph the seconds hand advances 5 times a second, the slower and more audible rate of an older design.

3970P_Breguet stands on its own in this catalogue — no other reference here shares its base number. It pairs a pink dial with a platinum case. Beyond the time it carries a chronograph and a perpetual calendar.

The CH 27-70 Q is the perpetual calendar chronograph of the Patek Philippe refs 3970 and 5970, made from 1986 to 2011. It is a Lemania 2310 base with Patek's own calendar module. It powers 34 watches in this library. The 2310 is the column-wheel hand-wound chronograph Lemania designed in 1942, and the [Lemania piece](/blog/the-lemania-2310) explains how the same movement came to sit in a Patek and an Omega Speedmaster. Patek took the ébauche, reworked and finished it to its standard, and mounted a perpetual calendar with moon phase on top: 24 jewels, a 60-hour reserve, a slow beat of 18,000 vph, and a 30 mm diameter. The CHR 27-70 Q added a split-seconds mechanism for the ref 5004. It was the last Patek perpetual calendar chronograph on an outside base; the in-house [CH 29-535 PS Q](/calibers/patek-philippe-ch-29-535-ps-q) replaced it in the 5270 of 2011. Every reference here is a [Grand Complication](/brands/patek-philippe/grand-complications): 22 in the 36 mm ref 3970 of 1986 to 2004 and 12 in the 40 mm ref 5970 of 2004 to 2011, in yellow, white and rose gold and platinum. Seven are limited editions, and the glossary defines the [perpetual calendar](/glossary/perpetual-calendar). The [CHR 27-70 Q](/calibers/patek-philippe-chr-27-70-q) is the split-seconds version, and the [CH 27-70](/calibers/patek-philippe-ch-27-70) the same base without the calendar in the ref 5070.

33 other watches in the library run the Patek Philippe CH 27-70 Q.

Patek Philippe

Perpetual Calendar Chronograph 3990 Platinum / Slate

3990P-XX1 · 36 mm

Patek Philippe

P-001 Perpetual Calendar Chronograph 5971 Diamond

5971 · 40 mm

Patek Philippe

Perpetual Calendar Chronograph 5971 Sapphire

5971/11P-101 · 40 mm

Patek Philippe

J-001 Perpetual Calendar Chronograph 3971

3971 · 36 mm