Swiss thin watch with minimized movement design Circa 1900

Open faced pocket watch by Edouard Koehn
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A Swiss ultra-thin 18 carat gold pocket watch from Geneva, circa 1900.
18 carat gold case; off white signed enamel dial with Roman hours, sunk subsidiary dial for the seconds and Breguet hands; three-bridge movement and a screw compensation balance. The extremely flat case is less than 9 mm high and contains an unusual, minimized movement design.
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Diameter: 48 mm
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Weight: 58 g
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Signed: Edouard Koehn à Geneve