After Leica’s success with their 35mm rangefinder cameras, optical manufacturer Carl Zeiss wanted a piece of the pie. They introduced their Contax rangefinder in 1932, immediately making themselves the leaders in photographic technology in Germany.
The Contax rangefinders featured a combined rangefinder/viewfinder decades before Leica competitors, and also featured a vertical metal focal plane shutter decades before this would become standard. Contax rangefinders also feature a dual bayonet lens system with an internal and external bayonet for different focal lengths.
After World War II, the Soviet Union seized the Zeiss Ikon plants in Dresden as well as Leica factories. They began to produce their own versions of the popular Leica and Contax rangefinders with looser machining tolerances. The Contax rangefinders were replicated in Kiev, Ukraine.
Because of this, there are many Soviet lenses available for the system on top of offerings from German companies like Carl Zeiss, Hugo Meyer, Schneider-Kreuznach, and Voigtländer.