Even if some of his personal records dated 1796 mention chronometers made earlier, most probaly in the years of 1780, it is not until 1815 when Abraham Louis Breguet was appointed Horloger de la Marine that he started to develop a commercial interest in producing Marine Chronometers. The production really developped between 1817 and 1818 at the approximate cost of 2 000 FF (French Francs) for each piece. Most of production was made with two-day power reserve movements, eight-day models were rarer and constructed differently. In order to obtain a uniform running for eight day models, Breguet used the fusee in place of the second barrel as it had been developed for two-day models. The fusee and barrel were placed in between two plaques to contain the necessary power. All Marine Chronometers from that period can be seen as horological master works of art, no two are identical; today they can be considered the perfect object for a drawing room's decoration, as the ultimate precision timekeeper. Abraham-Louis Breguet would open a prosperousera with the Marine Department, which paid very high prices for these instruments of precision, the relationship would follow on both with his son and grandson, even more extensively the firm Breguet developped new devices for the French Aeronavale during the course of the 20th century, such as the famous military flyback chronograph wristwatch the Type XX.