English silver chronometer pocket watch Circa 1792

Open-faced chronometer with YZ balance
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An important pocket chronometer of the second kind with YZ balance, circa 1792.
Silver consular case with case maker’s punch mark JB WW. Enamel dial, radial Roman hours, auxiliary seconds, blued spade hands. Full plate movement, firegilt, numbered, signed, screwed chatons, chain/fusee, moulded pillars, Arnold’s spring detent escapement, YZ balance with three cylindrical weights on threaded rods and three screws, free-sprung gold balance spring with a terminal curve, finely engraved and pierced balance cock, chatoned diamond endstone on balance.
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Diameter: 51 mm
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Weight: 135 g
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Signed: John Arnold & Son, London