Swiss steel chronometer with 55h power reserve Circa 1900

Gentleman’s fine open faced pocket watch  
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A gentleman’s very fine pocket watch with 55h power reserve indicator and chronometer balance  with extensive documentation, circa 1900. Steel case, blued, polished. Enamel dial, radial Roman hours, auxiliary seconds, spade hands. 1/2 plate movement, frosted, gilt, “Brevets Deposé”, bimetallic chronometer balance with 2 screws and 2 weights.
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Diameter: 51 mm
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Weight: 94 g