French gold verge with enamel miniature portrait Circa 1810

A French gold and stone set key wind pocket watch with enamel miniature portrait by Helsen, Paris, circa 1810. Gilt full plate fusee verge movement, pierced and engraved balance bridge, silver regulation. White enamel dial, black Roman numerals, black outer minute divisions, winding aperture at 2 and blued steel hands. Polished open face consular case, miniature enamel portrait to back depicting a lady within a stone set border, outer three colour gold foliate border. Dial and movement signed, case stamped ‘FT’.
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Diameter: 31 mm
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Signed: Helsen Paris