The Jupiter-8 is 50mm / f:2 Russian camera lens made by KMZ during the Soviet era. It was made to fit a number of different camera makes. It was available in the M39 lens mount, or "Leica thread mount", a bayonet mount to fit early Zeiss Contax cameras. It is a copy of the prewar Zeiss Sonnar 50mm f2.
6 elements in 3 groups
Distance scale: 1m to infinity
Mount: M39, Contax bayonet
Compatible with Leica M mount with adapter ring