Rare English silver open faced pocket chronometer Circa 1802

Silver chronometer by John Roger Arnold
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A rare English silver open faced pocket chronomter, circa 1802. Gilt finished chain fusée movement, Arnold spring detent escapement with the detent set into the top plate, bimetallic Z balance with compensation weights, gold helical spring with diamond endstone, freesprung. White enamel dial with Roman numerals, blued steel spade hands and subsidiary seconds. Plain case. Dial and and movement signed, case stamped with maker’s mark DW (Daniel Walker) and London date letter for 1802.
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Diameter: 63 mm
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Signed: Arnold 1871 – Jn.R. Arnold Invt et Fecit London