French silver astronomical verge pocket watch Circa 1810

Silver open faced verge watch by Ferdinand Berthoud
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Extremely rare French open faced astronomical pocket watch with display of sunrise, sunset and number of hours of sunshine, circa 1810. Signed verge movement. Original white enamel dial with decentralized time display, display for months, month length, date and extremely rare display for sunrise, sunset and sunshine duration depending on the month, blued steel hands. Plain case, reeded midsection, Paris silver punch.
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Diameter: 54 mm
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Weight: 119 g
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Signed: Ferdinand Berthoud à Paris
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Verge pocket watches with such an astronomical complication are very rare. A similar watch with the same astronomical display was auctioned by Antiquorum in 2008, estimated CHF 45.000 – 55,000.