Gold astronomical watch with virgule escapement Circa 1810

Historically important rose gold astronomical watch by Samuel Roi & Fils
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An impressive and historically important French rose gold open faced atronomical watch with virgule escapement, sunrise, sunset and sectorial type equation, circa 1810. Gilt finished full plate virgule movement, chain fusée, pierced and engraved scroll decorated balance cock. White enamel dial, eccentric hour dial with Roman numerals, gold arrow hands, outer ring calibrated for the sectorial type equation, indicating Soleil Retarde (sun regressing) and Soleil Avance (sun advancing), a dark blue panel illustrating the changing horizon moving in unison with the sun, central hand with sun shaped pointer, kidney shaped aperture revealing a golden sun over translucent blue enamel sunburst decorated background, outer 12 hours calibration and Lever du Soleil (rising of the sun) and Coucher du Soleil (sunset) indication, two subsidiary dials for month and number of days and date. Plain case. Case numbered, dial and movement signed.
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Diameter: 59 mm
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Signed: Sl Roi & Fils