The device for measuring time intervals applied to the Aero-Compax models was patented in Switzerland on December 15 1944 under No. 235608.This model bears a single-coloured bezel some others have a black and white bezel for day-time and night-time hours.This watch is the later version of the traditional Aéro-Compax Chronograph in which the small memory display dial is replaced by a revolving bezel numbered from 1 to 24.Similar watches are published in Universal Genève 100 ans de Traditions Horlogères by Italo Bonifacio and Laura Rivoltapp. 68 and 69.