The ref. 3970 is one of the most stunning grand complications ever produced by Patek Philippe and certainly the last truly vintage one.

The reference 3970 was introduced in 1986 as the successor to the legendary and ultra-collectible reference 2499 perpetual calendar chronograph. The reference was produced for an impressive 18 years, before it was replaced by the updated ref. 5970. The introduction of the 5970 marked the end of an era of an era, with Patek shifting towards housing its grand complications in significantly larger–and thus more modern looking–cases.

This ref. 3970ER (E = étanche, which means waterproof in French; R = rose gold) is a third series execution dating back to 1993. The watch features a classically-sized 36 mm 18K rose gold case with pump pushers and a solid 18K rose gold case back. While a see-through case back was also delivered with the watch at the time of sale, it was never installed on the watch and the original owner lost it over time.

The dial on this 3970ER is a so-called transitional version with details from both the second as well as third series models. As is typical for the second series, the text on the dial features a thin font (which is especially visible at the 55 second position, which doesn’t touch the second hash marks) and the day and month discs contain serifs. On the other hand, the pointed baton indices and matching pointed baton hands are typical for the third series. Together, these details make for an interesting and collectible sub-variety of the 3970.

The dial features three sub-dials. The recessed sub-dial at the 9 o’clock position displays a running seconds as well as a 24-hour hand while the recessed sub-dial at the 3-hour position incorporates a 30-minute chronograph counter and a leap year indicator. Finally on the lower sub-dial we find a charming moon phase indicator, which is surrounded by a date complication.

The watch comes on a black alligator leather strap with an 18K rose gold Patek Philippe deployant clasp, a service box and service guarantee tag. The watch is accompanied by an extract of the Patek Philippe archives.