Swiss stainless steel pocket tachymeter chronograph Circa 1907

Pocket chronograph with 5-colour-multiscale dial by Omega
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A Large Swiss stainless steel keyless-winding pocket watch for drivers with chronograph, minute recorder, and patented multiple tachometer scales dial, Chrono-Tachymeter, Cadran Brevetè SGDG, circa 1907-1910.
This watch has two horological complications: – 1/5 second chronograph (activated by the single round push-piece located on the winding-crown) with patented multiple multicolour Archimedean spiral telemetric scales graduated for 140 kilometres; – Half-instantaneous 15-minute recorder (subsidiary dial at 12 o’clock).
Gilded brass movement, going barrel, straight-line equilibrated lever escapement, monometallic screw-balance and self-compensating Breguet hairspring, index regulator; chronograph work on the top plate. Special enamel dial SGDG Tachyzifferblatt with 5-coloured tachymeter scale, subsidiary dial for the seconds, subsidiary dial for the register, centre chronograph hand, Roman radial hours, and original pear hands. Round-shaped stainless steel polished case. Dial and case signed.
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Diameter: 59 mm
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Signed: Omega Cadran Breveté S.G.D.G
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Cadran Tachymétrique breveté S.G.D.G., système A.T.
This patented dial was specially made for car drivers. This dial indicates, without calculation, by simple reading, the car’s speed by the hour.
The système A.T. refers probably to the invention of the French Captain Arsène Thouvenin, Paris, and its Phonotélémètre (Swiss invention patent No. 10 870, dated July 13, 1895).