A GOLD CIRCULAR WRISTWATCH, Patek Philippe & Co., Genève, NO. 794890, REF. 2591, CIRCA 1966

18k, rhodium plated lever movement (Cal. 23-300) stamped twice with the seal of Geneva, 18 jewels, gyromax balance, adjusted to heat, cold, isochronism and 5 positions, blue satin dial with applied gold baton numerals, baton hands, brushed circular case with polished bezel and bar lugs, snap-on case back, case, dial and movement signed, with an 18k pink gold Patek Philippe buckle. 

Patek Philippe commenced production of the reference 2591 in 1957. Illustration of a similar example see "Patek Philippe Wristwatches", by Martin Huber & Alan Banbery, Volume 2, Second Edition, P. 295.