French gold diamond set skeletonized verge watch Circa 1766

Gold pendant watch with enamel portrait of a Royal lady by Lépine
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A very fine, rare French gold and rose cut diamond set open faced skeletonized verge pendant watch with a painted on enamel portrait of a Royal lady, circa 1766. Hinged, frosted and engraved gilt skeletonized plate movement with conical pillars, fusee and chain, verge escapement with micrometric potence adjustment, three armed brass balance with blued steel flat balance spring, index regulator, triangular single footed solid engraved cock, rose cut diamond set silver filigree applied plate set with an oval painted on enamel portrait of a royal lady wearing a blue dress and red robe with ermine collar. White enamel dial with Roman numerals intersected by rose cut diamond set indexes, outer minute track with five minute Arabic numerals and original gilt Louis XV hands. Case glazed to both sides, bezels rose cut diamond set, band engraved with a repeated pattern. Dial signed.
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Diameter: 40 mm
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Signed: Lépine à Paris
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The enamel portrait possibly represents Princess Marie Thérèse Louise of Savoy-Carignan, Princess de Lamballe, an Italian-French courtier, aristocrat of the House of Savoy and royal confidante to Queen Marie-Antoinette. Her killing sparked a movement of anti revolutionary propaganda, which ultimately led to the development and implementation of the Reign of Terror. 
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Frederick-Louis Ducommun is recorded as working in Geneva in the late 18th and early 19th centuries.
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Jean Antoine Lépine (1720-1814), son of Jean, was born on 18 November 1720 at Challex, a small village a few kilometers north of Geneva. After having worked for some time at the establishment of Decrose, in the Grand Saconnex in the suburbs of Geneva, he arrived in Paris in 1744. A workman for André Charles Caron, ‘Horloger du Roi’ and father of Beaumarchais, he married his employer’s daughter in 1756 and was received Master in 1765. He was appointed ‘Horloger du Roi’ (watchmaker to the King) about 1765. In 1766 he succeeded Caron and appears on the list of Paris clockmakers of that year as: Jean-Antoine Lépine, Hger du Roy, rue Saint Denis, Place Saint Eustache. In 1772, Lépine established himself in the Place Dauphine, in 1778- 1779, Quai de l’Horloge du Palais, then in the rue des Fossés Saint Germain l’Auxerrois near the Louvre in 1781 and finally at 12 Place des Victoires in 1789.