Unusual French nickel cylinder pocket watch Circa 1900

Nickel watch with a calculator
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Unusual French nickel keyless pocket watch with a calculator, circa 1900. A polished case, hinged case back, inner classed back to view the movement. White enamel dial with painted radial Roman numerals, outer minute track with five minute red Arabic markers and silvered revolving calculator scale and blued steel spade hands. Gilt brass movement, cylinder escapement, plain brass three arm balance, flat balance spring.
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Diameter: 60 mm
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Signed: Meyrat & Perdrizet, Breveté S.G.D.G.  Seloncourt France
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Accompanied by instructions (in French)