Jupiter-8M 50mm F/2, USSR Lens For Kiev, Contax RF mount! s/n: 6617578

It is a copy of the Carl Zeiss Sonnar 50mm f2.0. Focal length: 50mm. Also at the very edge of the front lens, under the rim, there is a factory defect, it looks like a chip, but it is outside the visible area (see photo).

eBay