Swiss Chronographe Antimagnetique watch Circa 1915

Silver cased pocket watch with an extract from the archives
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A very fine early single button numbered chronograph ‘Compteur’, made by Longines in Saint-Imier, Switzerland, circa 1915. The original silver open faced plain case with a number that matches the one on the movement has a dust cover with the inscription Chronographe Antimagnetique and is also engraved with seven Grand Prix medals.
The white enamel dial has black Arabic numerals for the hours, a blue tachymeter scale, a red telemeter scale, a 30-minute counter at twelve o’clock and fine original gold hands. The movement has a very fine calibre, precision lever escapement with an intermediate wheel chronograph and calibre 19.73N.
Dust cover, dial and movement are signed.
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Diameter: 52 mm
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Weight: 99 g
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Signed: Longines  
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According to the extract from the archives delivered as a pilot’s chronograph to the company Blum, Longines’ agent in Italy at that time.
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Originally the movement left the Longines plants in an “aluminium transport case for pilots” and was delivered to the Longines agency Blum in Italy. Longines also supplied these movements to the U.S. Army.