Swiss heavy 1/10th split second chronograph Circa 1965

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 rhodium plated 2/3 plate movement with Geneva striping decoration, a lever escapement, split second chronograph, high speed oscillator, the finest matted bevelled steel chronograph parts, a ratchet wheel, ground and bevelled double hand tong with a separate ratchet wheel for the split second chronograph, a going train with constant force, screw compensation balance, balance spring with inner terminal curve, an index spring fine adjusting device, a hack feature and shock protection for the balance.

Dial signed, case and movement signed and numbered. Accompanied by the original, signed leather carrying case and original, numbered wooden transport box.
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Diameter: 66 mm
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Weight: 298 g
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Signed: Longines
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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.”