The Leica M3 is a 35 mm rangefinder camera by Ernst Leitz GmbH (now Leica Camera AG), introduced in 1954. It was a new starting point for Leitz, which until then had only produced screw-mount Leica cameras that were incremental improvements to its original Leica (Ur-Leica). The M3 introduced several features to the Leica, among them the combination of viewfinder and rangefinder in one bright window, like on the Contax II, a bayonet lens mount, and rapid film advance lever. It was the most successful model of the M series, with over 220,000 units sold by the time production of the M3 model ended in 1966.