English gold chronometer with interesting movement Circa 1875

Pocket chronometer with special winding
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A heavy pocket chronometer with very interesting movement and special winding, made in London, England, circa 1875. This plain full hunter cased watch is made of 18 Carat gold and bears London hallmarks from 1875 and the case maker’s hallmark JM. The white enamel screwed dial has Roman numerals for the hours, a subsidiary dial with Arabic numerals for the minutes at 6 o’clock and blued steel hands. The chronometer movement is very interesting with a special winding mechanism and a rocker detent escapement.
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Diameter: 53.5 mm
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Weight: 120 g
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Signed: No name