Swiss heavy 1/10th split second chronograph Circa 1968

Stainless steel Nonius split second chronograph
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A heavy Swiss stainless steel open faced precision split second chronograph, the Nonius, made by Longines, circa 1965. The polished case with a screwed on back. Silvered dial with Arabic hours, an outer minute track, 30 minute counter at 12 o’clock, constant seconds at 6, a white Arabic scale for tenth of a second timing, a yellow Vernier/Nonius scale from 0-9, an orange Nonius hand and black sword hands.

The 3/4 plate movement has a lever escapement and nickelled steel Guillaume balance. Dial, case and movement signed. Accompanied by the original leather carrying case.
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Diameter: 66 mm
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Weight: 298 g
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Signed: Longines 
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The present split second chronograph has been used at world-class sporting events like the Winter Olympics in Grenoble, France, since 1968. According to Longines, this timepiece with movement caliber 262 was the most precise watch they ever produced. The Vernier scale is a Longines patent used in this watch only.
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“Before introducing electronic time measurement, watch designers tried one last time to defy the triumph of electronics by creating a mechanical watch that incorporated all major technical accomplishments of its time. Their endeavours culminated in the calibre 262. All prerequisites for a precision watch were met: a large movement (∅ 57 mm), nickel steel Guillaume balance, antimagnetic Nivarox hairspring with inner and outer terminal curves. Swan neck regulation and a fine regulator for setting the time to the second went without saying, and the balance wheel frequency of 36.000 alternations per hour guaranteed absolute precision. Cut and bevelling matched the standard of the movement design. However, the main attraction was using a constant force mechanism. Renowned watchmakers such as Harrison, Breguet, Dent and Richard, to name a few, had concerned themselves with the constant force mechanism and the crown winder in their time.”