Interesting Swiss 18K gold pocket chronometer Circa 1860

Gold open faced chronometer
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A very interesting and very fine Swiss 18 carat gold open faced pocket chronometer, circa 1860. Chronometer movement, very rare winding mechanism, chain/fusee, pivoted detent escapement, solid gold escape wheel, screwed gold chatons, helical hairspring. White enamel dial with Roman hours and outer minute divisions, subsidiary seconds, blued steel hands. Engine-turned case, reeded band. Case numbered.
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Diameter: 49 mm
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Weight: 112 g
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Signed: No name