The Fontainemelon 158 is a manual-wind chronograph movement that was produced from 1937 to 1970, with over 3.5 million units manufactured during this period. It incorporates various chrono mechanisms, allowing for different sets of functions. The interchangeable nature of its parts sometimes led to the production of series with components from different calibers. Notable features include a 60-second and 30/45-minute chronograph, sub-second display, and cam switching mechanism.