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 Ministry of Defence, Hydrographic Dept. – executed legendary “fishtail” caliber – with original wooden box, circa 1917.
Steel polished case with reeded screw back and military engraving. 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: 101 g
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Signed: International Watch Co.
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Fishtail-caliber
This is one of the most successfull 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.