Rare silver complicated astronomical pocket watch Circa 1780

One of the earliest known astronomical watches
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Extremely rare and technically highly interesting astronomical pocket watch with an early perpetual calendar, moon phase, moon age and seconds display, Quantième Bisextile, circa 1780.
Full plate movement, verge escapement, chain/fusee, No.7072. Original enamel dial, inscribed Bisextile, with Roman radial hours, outer minutes track with Arabic fifteen minutes numerals, rose gold hands, subsidiary dial for the seconds at 6, and six astronomical complications: extremely rare perpetual calendar with 4 × 12 months; weekday; date; month with indication of the month length of 28-31 days; moon phase and moon age. Unusual silver case, back with relief of St. George Slaying the Dragon.
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Diameter: 57 mm
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Weight: 146 g
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Unsigned.