French gold, enamel and gem set watch with calendar Circa 1780

Gold verge with large gem in the centre
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A fine French 18 Carat gold, enamel, diamond and gem set pocket watch with calendar, circa 1780. Louis XV case, rope twist bezels, the back enamelled in imitation of jasper overlaid with a silver rosette set with irregular cut diamonds and a large gem in the centre. White enamel dial with radial Roman numerals, outer minute track and Arabic five minute numerals, inner calendar ring and gold beetle hands. A matte gilt full plate movement, ring turned pillars, fusee and chain, verge escapement with micrometric potence adjustment, three arm brass balance, flat balance spring, continental cock with steel end plate and a silver regulation dial. 
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Diameter: 38 mm
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Signed: No name
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Missing some stones and the minute hand.