Unusual German silver astronomical cylinder watch Circa 1780

Watch with stoppable dead centre seconds and half second beating balance
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An extremely fine, rare and unusual German silver astronomical cylinder watch with stoppable dead centre seconds, exposed mainspring and large half second beating balance, circa 1780. Full plate gilt finished cylinder movement, going barrel with exposed mainspring, half second beating five armed brass balance, the mainspring and balance secured by a pierced and scroll decorated circular plate, index regulator. White enamel regulator style dial, outer 60 seconds indication for the dead beat centre seconds with stop/start lever in the band, small hour dial with Arabic numerals, outer five minute divisions, two subsidiary dials for date and day and day, night, time from moonrise to moonset, gold arrow hands. Large plain case. Case stamped H 27, dial and movement signed.
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Diameter: 62 mm
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Signed: Hahn Echterdingen