French deck chronometer with footed detent escapement Circa 1840

Brass marine deck chronometer by Henri Motel
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A very fine and rare French, marine deck chronometer with spring footed detent and 40 hour power reserve, circa 1840. Three-tier mahogany deck box, the upper section with a numbered bone plaque, brass case en forme de tabatière secured inside the mahogany box, screwed down brass bezel. Matte silvered dial, radial Roman numerals, outer minute track, subsidiary seconds, power reserve sector below 12. Blued steel Breguet hands.
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Brass, three-quarter plate movement, spotted decoration, reverse fusee and chain, Harrison’s maintaining power, the barrel under a separate bridge, Earnshaw-type chronometer escapement, spring footed detent, two-arm cut bimetallic compensation balance with sliding cylindrical temperature weights and meantime adjustment screws, free-sprung blued steel helical balance spring, diamond endstone. Dial and movement signed, case numbered. Property of an American Collector.
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Dimensions: 115 x 98 x 62 mm
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Signed: Henri Motel,  Horloger de la Marine Royale
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The case has some scratches, also the dial has some scratches and is oxidized.
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Onésime Dumas (1824-1889) Was Louis Berthoud’s grandson and the nephew of Henri Motel. He was placed by the Government, in 1837, as a pupil to Louis- Frédéric Perrelet, then in charge of the Ecole des Horlogers de la Marine, since 1832. When Perrelet resigned in December 1839 for health reasons, and Charles-Auguste Berthoud was appointed as his successor by the Ministre 295 de la Marine to complete the instruction of his pupils, Onésime Dumas already had two and a half years of apprenticeship. When he left the school, he worked for a short period with Motel. Therefore, the very first chronometers made by Onésime Dumas were very similar to those produced by Louis Berthoud and later by his two sons.
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Working with his uncle, he made a few chronometers with the highly refined calibre which ensured the fame of Henri Motel. He then succeeded to Gunnery in Saint-Nicolas deal Ermont, in 1851. The chronometer No. 421, produced the same year, carries both their signatures. He employed between 12 and 15 craftsmen and exhibited precision horology at Rouen in 1856. He signed “Dumas Successeur de Gunnery”. His name was given to a new full-plate calibre, very much inspired by the English style, not as elegant nor refined as that of Motel, but less expensive to produce, robust and reliable. It was adopted by most other French makers. Literature: J.-C. Sabrier: “La Longitude en Mer à l’Heure de Louis (detail of the movement) Berthoud et Henri Motel”.  Fr Louis Berthoud’s grandson and nephew of Hen