Fine Swiss platinum open faced chronograph with register Circa 1928

Platinum lever pocket watch
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A fine and very rare Swiss platinum open faced keyless pocket watch with chronograph and instantaneous 30 minute register made by Vacheron Constantin SA in Geneva, circa 1928. A solid, polished and plain case. Matt silver dial with Arabic hour numerals, an outer minute track with additional fifth of a second divisions and Arabic five minute numerals, subsidiary seconds at 6 o’clock, a 30 minute register at 12 and gold Breguet hands. A rhodium plated movement, 23 jewels, straight line lever escapement, cut bimetallic compensation balance, Breguet balance spring and Vacheron & Constantin micrometre regulator after Patent CH 101652, registered on November 1, 1923. Dial, case and movement signed.
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Diameter: 46 mm
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Signed: Vacheron & Constantin Geneva Suisse