German double wheel duplex escapement repeater Circa 1820

A gentleman’s large quarter repeating pocket watch
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A gentleman’s extremely rare, large, quarter repeating pocket watch with double wheel duplex escapement and date, circa 1820.
18k gold case, polished, case maker punch mark “HR”, pusher for repetition via pendant. Enamel dial, radial Roman hours, auxilliary seconds, blued Breguet hands. Full plate movement, keywind, firegilt, signed, 2 hammers, 2 gongs, chain/fusee, balance stop device, three arm brass balance, blued balance spring with bimetallic compensation curb on the index hand and additional fine adjusting device.
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Diameter: 60 mm
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Weight: 162 g
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Signed: Johann Baptist Mahler à Obergünzburg