American 18k gold open faced cabriolet watch Circa 1857

Cabriolet watch with three-toothed duplex escapement by Charles E. Jacot
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A fine, extremely rare American 18-carat gold open faced cabriolet pocket watch with three-toothed duplex escapement, patented July 1852. Frosted half-plate movement, ten jewels, two in screwed gold chatons, going barrel, Jacot’s star duplex escapement with three teeth and three vertical impulse pins between, beat of 21,600 per minute, cut bimetallic compensation balance with timing adjustment screws, blued steel flat balance spring, index regulator. Hinged gold cuvette with engine turned border, inscribed John P. Buchner, 1857. White enamel dial with Roman numerals, outer minute track, subsidiary seconds and original blued steel Breguet hands. Outer case detachable and reversible, the back with engraved vacant cartouche, the interior engine turned, reeded band, the inner case engine turned, band with engraved stylized leaf decoration. Movement signed.
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Diameter: 56 mm
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Signed: Chas. E. Jacot
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The star duplex escapement has an escape wheel in the shape of a three-pointed star with three vertical impulse pins placed on a small platform between the points of the star. The escapement beats at 21,600 per minute, an unusually high and accurate beat for the period.
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Charles E. Jacot (1817-1897) worked in La Chaux-de-Fonds, Le Locle, Baltimore and New York. He was a prolific inventor and innovator, especially in escapement work. At the age of 19, he visited his cousin, the son of Abraham Perrelet, in Le Locle and became involved in watchmaking. In 1837 he went to New York City, where he would remain for 20 years. Jacot invented a modification of the duplex escapement with a jumping seconds hand, known as the ‘Jacot Duplex’, used extensively in watches made for the Chinese market. While in America, he registered 12 American patents for perfecting the construction of watches. An important patent, registered on July 20, 1852, was for the star duplex escapement. Charles Jacot died in August 1897.