French quarter repeating à quatre couleurs watch Circa 1770

Very fine gold pocket watch montre à toc et à tact
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An extremely rare, fine gold enamel quarter repeating à quatre couleurs verge pocket watch montre à toc et à tact with matching gold enamel chatelaine, circa 1770.
18-carat rose gold case with paste-set bezel, dot patterned band, on the back cover a polychrome enamel medallion with the miniature portrait of a noble lady drinking chocolate, paste-set border, framed by paste-set and three-colour gold flower tendrils, paste-set thumb piece and rear bell. Matching gold chatelaine, silver, marcasites and gold, two polychrome enamel miniature portraits of noble ladies, the signet and watch key, length: 120 mm. Enamel dial with Roman radial hours, Arabic minutes and Louis XV hands. Full plate movement, keywind, fire gilt, signed, chain/fusee, solid movement pillars, three-arm brass balance, blued balance spring, fine florally engraved and pierced balance bridge.
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Diameter: 42 mm
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Weight: 66 g
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Signed: Berthoud à Paris
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This watch was made by Berthoud à Paris when the firm was already well established. It had been founded by Ferdinand Berthoud (1727-1807), who emigrated to Paris from Switzerland in 1747. Berthoud was not only an eminent watchmaker but also the author of several books on the history, theory, and practice of watchmaking.