This is a fine and rare 18K gold reference 2509 watch, manufactured by Patek Philippe, Genève circa 1956.
Ref. 2509 and its twin sibling – Ref. 2508 – are considered the apex of Patek’s mid-century case design. Ref 2508 was the manufacture’s first waterproof screw-back case for a time-only watch, and Ref 2509 followed with the same distinct ten-sided design back cover that screws in water-tight. Whereas the majority of Ref 2508s used an indirect center-second movement, Ref 2509 used caliber 12-400 movement with subsidiary dial to count the seconds. This gives Ref 2509 an old fashioned look.
Cailber 12-400 is fitted with a straight-line lever escapement, a monometallic balance adjusted for heat, cold, isochronism and five positions, a self-compensating Breguet balance-spring, and a micrometer regulator. It is decorated with the Geneva seal.
The circular water-resistant screw-in case back, dust cap, 18K gold buckle, case, dial and movement are all signed.The case appears unpolished with razor sharp edges and a deep hallmark under the crown. 35.5mm diam.
