The present watch is the largest and most complex of the "Chrono-tachymeter" watches by Omega and is extremely rare in a gold case. The term "Chrono-tachymeter" refers to the dial with its extended tachymeter scale capable of timing speeds both slow, 10.5 kph, to speeds that were not yet achieved by the fastest cars of the day, 200kph. The 15-minute counter includes five colored zones corresponding to the colors of the tachymetric scale and indicates which sector of the scale is to be read. Most tachometers from this period that were graduated to such high numbers were marked UPH as they were more commonly used for production timing. At the time this watch was made such speeds were encountered only in scientific experiments as aviation was in its infancy. This type of dial could be found on both wrist and pocket chronometers from this period. Cal 19''' LOB L = Lépine O = Omega caliber B = 15-17 jewels, Breguet balance spring adjusted to less than one minute per day. Similar watches are described and illustrated in "Omega - A Journey Through Time", Marco Richon, 2007, p. 520-522.