Rare French double wheel Debaufre escapement Circa 1790

Very rare double wheel Debaufre
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A very rare French double wheel Debaufre escapement with pirouette in a silver gilt open face case, circa 1790. Full plate gilt key wind fusee movement, polished steel Geneva stop work. Harrison’s maintaining power. Large engraved sector cock, polished steel regulator. Very large plain five arm steel balance beating seconds, blue steel spiral hairspring. The escapement and balance connect by a wheel and pinion pirouette. A very rare form of Debaufre escapement with two escape wheels, each with four teeth mounted on a pinion facing each other with the staff of the pirouette between them. These act alternately on a polished steel disc carried on the arbor of the mock pendulum. Signed white enamel dial with center seconds, small chapter of Arabic numerals at twelve o’clock, blue steel seconds hand and gold hands. At the lower edge of the dial, a glazed circular aperture revealing a mock pendulum moving in time with the balance. Engine turned silver gilt open face case hallmarked London 1828. Ribbed middle, reeded pendant and bow. In a gilt tooled red Morocco case from Camerer Cuss and Co, 56 New Oxford Street. Their book was first published in 1967.
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Diameter: 58 mm
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Depth: 13 mm
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Signed: Dubois et Fils
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A very rare escapement combined with other interesting features. This watch is shown on pages 208 and 209 of the Camerer Cuss Book of Antique Watches. The book notes that the case is Swiss, the hallmarks having been applied when the watch was imported into England. The plate is engraved ‘I.H. London’, perhaps the importer. The debaufre escapement is also known as a chaff cutter, Ormskirk  or club footed verge. It was the first frictional rest escapement invented by Debaufre in 1704. Rarely used until it was taken up by Lancashire makers early in the 19th Century. The doubled wheeled variation is the first we have seen. Dubois et Fils, Paris 1770 – 1800, center seconds pirouette watch movement in the Guildhall Museum.