Swiss gold watch set in 10 US Dollar gold coin Circa 1970

Gold keyless lever coin watch by Piaget 
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A very fine Swiss, 10 U.S. Dollar 18k gold coin dated 1906 with a concealed watch, circa 1970. Double case, coin opening with a push-piece concealed in the band, three-body hinged inner case. Satine silver dial with painted baton indexes. Blued steel baton hands. A rhodium-plated, 18 jewels, straight-line lever escapement, monometallic balance, self-compensating flat balance spring, shock absorber, and a micrometre regulator. Dial, case and movement signed.
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Diam: 30 mm
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Signed: Piaget  Swiss
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The 10 Dollar version of the coin watch is much scarcer than the 20 Dollar model.