English chronometer with pivoted detent escapement Circa 1867

Open faced silver pocket watch by J.M. French
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A very fine English silver pocket chronometer, in good condition and fine quality, with pivoted detent escapement and hallmarks London, circa 1867.
Silver case with London hallmarks from 1867 “no. 40289“;  fine English chronometer movement with pivoted detent escapement, helical hairspring and screwed gold chatons; white enamel dial with Roman hours, sunk subsidiary dial for the Arabic seconds and blued steel spade hands. Movement signed.
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Diameter: 51 mm
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Weight: 112 g
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Signed: J.M. French, Royal Exchange London