Very rare Swiss sterling silver lever chronograph Circa 1910

Silver keyless chronograph by Omega
–
A fine and very rare Swiss sterling silver open faced chronograph keyless lever pocket watch with 15-minute recorder, tachometer and telemeter for 1 to 5 minutes base, circa 1910. Gilt-brass ¾ plate, straight-line lever escapement, cut bimetallic balance, blued steel Breguet balance spring, index regulator. Chronograph functions by a single button on the winding crown. Cuvette engraved with 12 Omega contest medals. White enamel dial with printed Arabic numerals, 1/5th seconds chronograph scale, subsidiary sunk dials for the seconds at 6 and the 15-minute register at 12, outer tachometer and five multicolour telemeter scales, original blued steel Breguet hands. Polished case, hinged back, bezel and cuvette. Dial, case and movement signed, case and movement numbered.
–
Diameter: 53 mm
–
Thickness: 15 mm
–
Signed: Omega Swiss Cadran Breveté S.G.D.G.