French gold watch with special enamelling technique Circa 1780

Gold open faced pocket watch by Berthoud
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An exceptionally fine French Louis XV-style 18K gold and enamel pocket watch with special enamelling technique and mother-of-pearl inlays, circa 1780.
Both bezels are set with faux mother-of-pearl half-pearls (partially damaged and worn), the case back with extraordinary polychrome enamel work, a raised putto and flowers on a translucent dark red guilloché ground. Signed verge movement. White enamel dial with radial Roman hours, outer Arabic five-minute numerals and presumably original Louis XV-style hands.
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Diameter: 39 mm
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Weight: 46 g
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Signed: Berthoud Paris