These watches were used by the Marine Nationale Iraneaise and the AeronautiqueNavale frantaise. Tests were made at the C.E.V. ( Centre d'Essai en Vol). These watches were the property of the State and it was very rare that they would be given to pilots. Each of these chronographs were overhauled every year either by the Dodane Manufacture or by the Service Officiel de Contrdle de la rnarche des montres deBesan{on ( Cetehor) . The symbol F. G. on the "end of warranty" (Fin de Garantic) and was together with the date of the next control. Chronograph Type XX and 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 be fitted on aircrafts. MoiihrsTi uettherefore introduced chronographs with registers and tachymetric 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 postwar aviator's watch. Though at first these watches were intended for the strict use of air forces, Breguet, in the 70 ' s, launched the seconde generation of then edited these models for civilians. Breguet's third generation of Type XX, Type XX Aeronavale, is now on the market. The peculiarity of the Type XX chronograph is that it features the retour en vol, 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 dashboards. The retour en vol device is a great ti me 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.