French gold and pietra dura open faced cylinder watch Circa 1835

Gold pietra dura decorated pendant watch 
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An exceptional, extremely fine and rare French 18 carat gold open faced pocket watch with matching pendant, circa 1835. Bridge movement, key winding, a flying barrel, cylinder escapement and three arm brass balance. A screw down gold cuvette. The eccentric dial with Roman hours on a black champlevé enamel chapter ring, central pietra dura decoration, inlays in a rosette pattern made of bloodstone, lapis lazuli, nephrite and white jade set in fine gold bars, moon hands. A case back decorated to match the dial with the same inlays made of bloodstone, lapis lazuli, nephrite and white jade set in fine gold bars in a rosette pattern, the band is alternately set with the same stones, case maker’s mark LS for Leopold Sécheret. Cuvette signed.
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Diameter: 37 mm
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Weight: 40 g
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Signed: Duponchel à Paris
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In contrast to the Italian pietra dura inlay work, in which the stones are put together in a frame, here each piece of hard stone is set in a gold frame, similar to cloisonné work. These cases and dials are remarkable not only because of their exceptional craftsmanship but also because of their skill in processing the thin plates accordingly. To our knowledge, less than ten other watches of this type are known to date.