French gold watch set in US 20 Dollar gold coin dated 1904 Circa 1920

Gold lever coin watch by Cartier
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A very fine and extremely rare French, 18K yellow gold U.S. 20 Dollar coin dated 1904 set with a concealed keyless watch, circa 1920. The case is made by European Watch and Clock Co., Inc., master mark EJ, coin opening with a concealed flange in the band, polished bezel with four screws, engine-turned ring around the dial. Matte silver dial with painted radial Roman numerals, outer minute track. Black baton hands. A rhodium-plated movement, Geneva striping decoration, 18 jewels, straight-line lever escapement, cut bimetallic compensation balance with eight adjustments, blued steel flat balance spring, index regulator. Dial and movement signed Cartier, Paris, case signed European Watch & Clock Co., Inc., France.
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Diameter: 34 mm
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Signed: Cartier  Paris