Swiss silver deck watch for the british Royal Navy Circa 1945

Silver deck watch by Vacheron & Constantin 
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A rare Geneva deck watch for the british Royal Navy  with original box, circa 1945.
Silver case, polished, silver dome, punch mark “FFBA” (Fédération des Fabricants de boites argent) dial is silvered, arabic numerals, central seconds,  blue spade hands, bridge movement, “broad arrow”, large Guillaume gold screw compensation.
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Diameter: 60 mm
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Weight: 154 g
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Signed:  Vacheron & Constantin  Genèva