Unusual German gold astronomical cylinder watch Circa 1800

Gold watch with stoppable dead centre seconds
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An extremely fine German, rare and unusual, large, astronomic, 18K gold pocket watch, circa 1800. Dead centre seconds, date and month calendar, day and night indication, exposed mainspring and large half-second beating balance. White enamel dial with small eccentric meantime dial, radial Roman numerals, outer dot minute divisions and Arabic quarter-hour numerals, outer dot seconds divisions and Arabic 15-second numerals, subsidiary dials for the date concentric with the months and their respective number of days, day and night dial concentric with astrological symbols. Gold arrow hands.
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A gilt brass full plate movement, engraved border, cylindrical pillars, going barrel with exposed mainspring enclosed within an aperture within the backplate, cylinder escapement, half-second beating five-arm brass balance, faceted red endstone, the mainspring and balance secured by a pierced circular plate above the backplate, index regulator. Dial and movement signed. Property of a European Collector.
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Diameter: 62 mm
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Signed: Hahn Echterdingen
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Hahn The brothers Hahn, Christian Gottfried (born 1769), Christoph Matthaüs (1767-1833), Johann Georg, and Immanuel, worked in the workshop of their father Philipp Matthaüs Hahn of Onstmettingen, Kornwestheim, and Echterdingen. Christian Gottfried and Christoph Matthaüs went on to become “Hofmechanikus” (court mechanicians) in Stuttgart. Christian Gottfried was later recorded in Berlin, Germany, and in America.