English silver watch with spring detent escapement Circa 1879

Silver chronometer with power reserve
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A rare silver open faced pocket chronometer with power reserve and helical hairspring, circa 1879. Three quarter plate gilt metal movement, spring detent escapement, helical balance spring, white enamel dial, radial Roman numerals, subsidiary seconds dial, power reserve indication at 12, silver case, hinged back, movement signed Benson, case hallmarked for London 1879, makers mark GJT.
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Diameter: 56 mm
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Signed:  W. Benson London