French 20K gold, enamel and diamond Louis XVI watch Circa 1775

Gold open faced verge pocket watch
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A Large French 20K gold and enamel pocket watch. circa 1775. A Louis XVI case, bezel released by a concealed pin-catch, engraved and set with diamonds, the back decorated with a repeating border pattern of flowers and the back blue enamel with applied diamond-set decoration. White enamel dial, black Arabic numerals, outer minute track, Arabic quarter-hour numerals and blued steel Breguet hands. An entire gilt plate movement, plain pillars, fusee and chain, verge escapement, three-arm brass balance, flat balance spring. Dial and movement signed Gregson, case signed Leton.
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Diameter: 60 mm
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Signed: Gregson  Paris
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The case with some lacking elements and the dial has a decoration of hairlines.