Swiss gold open faced chronograph pocket watch Circa 1940

Gold open faced chronograph watch
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A Swiss, yellow gold open faced chronograph watch, circa 1940. Lever movement, 17 jewels, bimetallic compensation balance, single-button chronograph mechanism.
Silvered dial, applied yellow gold baton indexes, yellow gold hands, engine-turned subsidiary dials for constant seconds and 30-minute register, outer minute track with black painted Arabic divisions, outermost blue tachometer scale, 18k yellow gold case, pusher through the crown, personally inscribed snap-on case back, case, dial, and movement signed.
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Diameter: 48 mm
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Signed: Rolex Genève