French gold two train quarter repeating lever watch Circa 1850

Very rare hunting cased lever with patented mnemonic dial by Charles Oudin
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A highly rare and unusual French 18 carat gold hunting cased two train quarter repeating keywound lever watch with independent dead centre seconds and patented mnemonic dial, circa 1850.
Gilt finished two train lever movement, bimetallic compensation balance, quarter repeating on two hammers onto a gong. Oudin’s patented Mnemonic dial on the gold cuvette, outer white enamel chapter ring with Breguet numerals and five minute divisions, central blued steel hand, inner date ring with Arabic 1 – 31 numerals indicated by means of a rotating blued steel disk. White enamel dial with Roman numerals and outer five minute divisions for the independent centre seconds. Engine turned, engraved coat-of-arms to the front and initials MS to the back, repeating slide and independent centre seconds. Case numbered 6650 and 335, dial signed in inlaid blue enamel Cadran Mnémonique par Charles Oudin Breveté, Médailles de 1806 à 1862, movement signed P. Sandoz & Fils underneath the dial.
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Diameter: 49 mm
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Signed: Charles Oudin Horloger de la Marine Palais Royal 52 Paris Cadran Mnemonique Brevete