Russian open faced ankerchronometer with calendar Circa 1910-1920

Silver ankerchronometer by B.F. Altschwager
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Extraordinarily large Russian silver open faced anker chronometer with calendar, circa 1910-1920. Presumably, two day anker chronometer movement with huge 21 mm chronometer balance. White enamel dial with fine hairline, Roman hours, Arabic five minutes, Russian weekday display, hand with date, subsidiary seconds and blued steel hands. Heavy, partly rubbed engine turned case, blanc cartouche on the back.
Dial and cuvette signed.

Diameter: 76 mm
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Weight: 325 g
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Signed: B. Altschwager St. Petersbourg
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Bernhard Friedrich Altschwager (1862-1931), St. Petersburg.
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A very rare piece in this size.