Rare metal Longines watch with 8 days reserve Circa 1920

Rare Longines eight days  pocket watch
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A very rare Swiss Longines metal open faced pocket watch with 8 days movement, circa 1920, movement with 19 jewels and fine adjustment, and 8-days-power reserve, caliber 19.41.
Gilt movement with cut bimetallic compensation balance.
White enamel dial with power reserve indication, subsidiary seconds, Arabic numerals and blued steel hands.metal housing, signed: Longines Chavanne Freres Tunis, high-functioning, very rare. It showed up today, very few pocket watches with the calibre 19.41. It is one of the rarest Longines calibres.
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Diameter: 51 mm
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Weight: 100 g
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Signed: Longines Chavanne Freres Tunis
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This movement is shown in book Les Mouvements de Montre de la Maison Longines.
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Reference 020000