These watches were used by La Marine Nationale et l'tldronaulique- Navale Francaise. Tests were made at the CEV (Centre dLssai en Vol). These watches were the property of the State and it was very rare that they would be given to the pilots. Each of these chronographs were overhauled every year either by the llodane Manufacture or by the Service Official de Cant role de In marche des montres de Besancon ( Cetehor). The symbol F.C. on the back case meant Fin de Garantie, and was combined with the date of the next control. Chronograph Type XXand the retour en vol device. Louis Breguet (1880-1955) developed a keen interest in aeronautics, conquering the air in 1907 in his gyroplane, the first helicopter in the world to leave ground with a passenger. Soon afterwards was established the "Louis Breguet" aircraft industry. Meanwhile, the watchmaking firm Breguet, saw a new opening and began producing watches for pilots or to he fitted on aircrafts. " Montres Breguet" therefore introduced chronographs with registers and tachometric scale and among their first clients were, of course, the American Air Force in 1918 and the "Louis Breguet" aircraft industry in 1922. The number of clients soon increased, especially in the fifties. The chronograph wristwatch Type XX, launched in 1954, became the most successful and most famous post-war aviator's watch. Though at first these watches were intended for the strict use of air forces, Breguet, in the 70's, launched the second generation of these, edited for civilianuse. Breguet's third generation of Type XX Aeronavale is now on the market. The peculiarity of the Type XXchronograph is that it features the retour en cal, or "instantaneous fly-back" device. This function highly appreciated by pilots and aeronautical authorities, was incorporated in all Type XX models and in chronographs to be fitted in aircraft dashbards. The relouren voldevice is a great time saver, reducing three actions to one, since it allows the chronograph hand to return to zero by simply depressing the lower push-button; consequently, the chronograph hand, back at zero, can restart immediately.