Silver English chronometer, power reserve Circa 1881

Silver pocket chronometer with power reserve
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A fine silver English open-faced pocket chronometer with power reserve and duo-in-uno balance spring, circa 1881, gilded half-plate movement, spring detent escapement, blued steel duo-in-uno balance spring, plain balance cock raised for clearance and with diamond endstone, fusee and chain, Harrison’s maintaining power, signed J. Hammersley 14 Barclay Road, Fulham, London.
White enamel dial, Roman numerals, blued steel spade hands, large subsidiary seconds, up-and-down indicator below 12 o’clock for the state of wind, inner bezel calibrated for 24-hours.
Plain silver case, the hinged back opening to hinged cuvette with winding and setting apertures, case with maker’s mark JTW in an oval.
cameo for James Thomas White.
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Diameter: 54 mm
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Signed: J. Hammersley 14 Barclay Road Fulham, London
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John Hammersley (1819-1901) was a notable springer and adjuster. In common with A. P. Walsh, Hammersley extensively used the duo-in-uno balance spring.

The finish of this watch is quite exceptional and the fact that it is key wound rather than keyless (high-quality key wound watches were becoming increasingly unusual by this date) suggests that it may have been intended as a deck watch or perhaps for land survey purposes. The unusual 13-24 hour zone engraved and filled with blue enamel on the reflector inside the front bezel of the case could support its use onboard ship.