Swiss extremely rare IWC Schaffhausen deck watch Circa 1917

Steel open faced deck watch by “IWC”  International Watch Co.
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An extremely rare Schaffhausen deck watch of the British Royal Navy, executed legendary “fishtail” calibre and centre seconds, circa 1917.
Steel polished case with reeded screw back. Signed enamel dial with Arabic numerals, centre seconds, “broad arrow”, and blued spade hands. Bridge movement so-called “fishtail calibre”, frosted, gilt, chatoned, with indirect centre seconds, “Patent 55231”, screw compensation balance and index spring fine adjusting device.
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Diameter: 51 mm
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Weight: 96 g
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Signed: International Watch Co.
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Fishtail calibre
This is one of the most successful watch movement designs ever made. The aesthetical beauty of this construction is unmatched. At the same time, this is one of the rarest IWC-works, of which only 600 pieces were produced.