Created in 1933 by Lémania, the manually wound chronograph calibre 33.3 CHRO is one of Omega’s most iconic movements. It was initially designed for single button chronographs, however in 1938 a version with two pushers was introduced. Very reliable an precise, the cal. 33.3 CHRO was in production until 1952, used in a variety of case materials and shapes.

The present chronograph ref. 2393 is distinguished by its large size case with elongated slim facetted lugs and the attractive two-tone silvered dial with blue telemetre scale calibrated for 20 km.

Telemetre scales are used to measure the distance of an occurrence which is both visible and audible. The chronograph hand is released at the instant the phenomenon is seen and stopped when the sound is heard, its position on the scale showing the distance in kilometres or miles separating the event from the observer.

This feature was most notably used for military purposes, where artillery forces can judge the distance of bombs that they are firing - or that are being fired at them. A civil use of the telemetre scale may include the judging of how far away a storm is by activating the chronograph when one sees the lightning flash. When hearing the thunder, the hand is stopped and shows the wearer the distance of the approaching storm.

A stainless steel ref. 2393 also with telemetre scale is described and illustrated in Omega – A Journey Through Time by Marco Richon, p. 538, pl. 2549, Calibre 33.3 CHRO on p. 532.