French 18K gold open faced lever chronograph Circa 1870

Gold chronometer with chronograph
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A very fine French 18 carat gold open faced pocket chronometer with chronograph, possibly a school watch, circa 1870. Glazed, precision movement with chronograph, exceptional experimental fine adjusting device, gold chronograph wheels, chronometer balance, lever escapement. White enamel dial with Roman hours, Arabic five minutes and outer chronograph scale, subsidiary seconds, blued steel hands. Plain case, enamelled monogram on the back. Dial signed, case numbered.
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Diameter: 50 mm
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Weight: 103 g
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Signed: A. Ecalle Paris