The Contrôle Officiel Suisse des Chronomètres (or the Official Swiss Chronometer Testing Institute) was established in 1973 in La Chaux-de-Fonds, Switzerland and is the organisation responsible for certifying the precision and accuracy of mechanical watches. To obtain COSC certification, a watch must undergo rigorous testing over 15 days in various conditions (including different temperatures, positions, and levels of magnetism). COSC-certified watches have passed these tests and keep time with a maximum variance of -4 to +6 seconds per day.