Omega "Cadran" Breveté S.G.D.G., Case No. 4342775, Ref. CH 543.19, Cal. 19'''CHRO, 54 mm, 117 g, circa 1910

A gentleman's rare pocket watch with chronograph and polychrome S.G.D.G. dial and tachy scale
Case: silver, polished. Dial: enamel, Arabic numerals, 15 min. counter, concentric tachy scale, spade hands. Movm.: 4/5 plate movement, frosted, gilt, very finely ground chronograph steel parts, ratchet wheel, screw compensation balance, index spring fine adjusting device.

S.G.D.G. Tachymeter Dial
The tachymeter dial allows the measuring of any speed between 10.5 and 140 miles per hour without the help of calculations.
15-minute counters starting with 5 individual minute segments in different colours to indicate which colour will show the speed on the spiral tachymeter scale.
Source: Marco Richon "Omega", 2007, p. 520-523