Swiss gold open faced chronograph pocket watch Circa 1940

Gold chronograph watch with open face by Rolex
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A Swiss, keyless winding, gold pocket watch with chronograph and minute recorder with open face, circa 1940.
Round shaped 18 Carat yellow gold case with patented snap on case back with screwed gilded metal insert. Case  back engraved in taille douce with the dedicacation Colegio Ward / al / Profesor, Director Técnico, Médico / 11918-40. /Dr P. O. Dezeo. Silvered dial, applied yellow gold baton indexes, yellow gold hands, engine turned subsidiary dial at 6 for constant seconds and 30 minute register at 12, outer minute track with black painted Arabic divisions, outermost blue tachometer scale, 1/5 second chronograph with single push piece (activated by a button located on the winding crown at) and telemetric scale graduated for 1 000 metres Case based on the Swiss invention patent No. 144 357, delivered on June 30, 1930, to Gabus Frères, Usines Safir, Le Locle, for a “Boîte de montre” (Watch case). Rhodium plated movement, going barrel, straight line lever escapement, compensated balance and self compensating Breguet hairspring.
Dial, case and movement signed. Accompanied with a copy of the invention patent.
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Diameter: 50 mm
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Signed: Rolex Genève