English silver verge watch with day & night indication Circa 1825

Open faced pocket watch by Thomas Maston
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An English rare one hand pair cased verge watch with retrograde hours and day & night indication, circa 1825.
Solid silver pair cases with watchpapers, matching London hallmarks 1825. Fire gilt verge movement with grotesque face and the main plate signed and numbered. Silver champlevé dial with day and night indication, rotating retrograde Roman hours indication, Arabic minutes and pink gold central minute hand.
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Diameter: 55 mm
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Weight: 150 g
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Signed: Thomas Maston London