Extra thin 18 Carat yellow gold open faced dress watch Circa 1956

Gold keyless lever dress watch 
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A very fine and extremely rare Swiss, extra thin, 18 Carat yellow gold keyless dress watch, circa 1956. A polished case, rounded bezel, triangular pendant, knife edge band. Matte silver dial with applied yellow gold baton indexes. Yellow gold baton hands. A rhodium plated movement, Geneva striping decoration, 20 jewels, straight line lever escapement, cut bi metallic balance adjusted to temperature and two positions. Blued steel flat balance spring.
Dial, case and movement signed. Property of a Swiss Collector.
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Diameter: 41 mm
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Signed: Vacheron & Constantin  Genève
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The dial is slightly rusted.
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The movement is made by LeCoultre for Vacheron Constantin was the flattest movement at the time. It was used by both Vacheron Constantin and Cartier.