Swiss/French rock crystal open faced keyless watch Circa 1916

Rock crystal watch accompanied by leather presentation box
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A very rare and elegant Swiss/French rock crystal, platinum, 18 carat gold, enamel and diamond set keyless pocket watch made by Cartier in Paris and the European Watch and Clock Co. in Le Sentier, circa 1916. Accompanied by a period gold tooled green leather Cartier presentation box. Rock crystal case with a diamond set platinum band and platinum triangular bow, yellow gold and white enamel bezel featuring alternate radial Roman hour numerals and flowerhead half hour markers. Silver, engine turned dial with outer minute track and inner Arabic five minute numerals on a brushed chapter ring, blued steel Breguet hands. A movement by the European Watch and Clock Co. Inc., rhodium plated with Geneva striping decoration, 19 jewels, straight line lever escapement, a cut bimetallic compensation balance with eight adjustments, blued steel Breguet balance spring and an index regulator. Dial signed Cartier, movement signed European Watch and Clock Co., case numbered on the bow.
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Thickness: 6 mm
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Diameter: 48.5 mm
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Signed: Cartier  Paris
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The dial is slightly oxidized.
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The European Watch and Clock Co. was established in the 1920s as a joint venture between Cartier and Edmund Jaeger of Jaeger-LeCoultre in Le Sentier, Switzerland.