A gold automatic perpetual calendar wristwatch with moon phases, Patek Philippe & Co., Genève, Movement No.770763, Case No. 2838643, Ref. 3940J, 1st Series, Circa 1986

18k, Cal. 240Q,  nickel lever movement, movement stamped with the Seal of Geneva, 27 jewels, Gyromax balance, free sprung regulator, 22k gold mini-rotor, silvered matte dial, applied baton numerals, three subsidiary dials indicating day combined with 24 hours divided into diurnal and nocturnal time, month combined with leap year indication and date combined with phases of the moon, circular snap back case, case, dial and movement signed, with 18k Patek Philippe buckle.

This model, Ref. 3940, was launched in 1986.

The present example is from the first series of this model and features a dial with no crossed leap-year indicator, a standard, non-deployant buckle and only one, solid case back.

It is believed that there were about 1300 of these models made from this series, and, as it was only made in such a variation for about two years, it is more rare than subsequent series.