The high officials o in the Air Force have imposed this condition as it was vital for pilots when they would fly over a beacon or when they had to land relying on the time given by the control tower. Such a demand may sound odd if one thinks about the evolution and sophistication of the present electronic outfits. Nonetheless, at that time, the reliability of the clock and watch making industry was a matter of life or death, the watch had become a flying instrument capable of replacing a failing on-board device. Among other requirements from the French National Defence’s specifications: an autonomy of over 35 hours, a maximum time difference of 8 seconds per any 24 hours. The difference was reduced to 0.2 seconds per minute and 0.5 seconds per half hour for chronometers. | 
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