Helios 44M 58mm f/2 Soviet Lens M42 #8000734 + Front Cap
(Focal length: 58mm (58.60 mm). Rear vertex focal length: 38.05 mm. Front vertex focal length: -34.25 mm. Distance from the first to the last surface: 39.80 mm. Resolution (0/10/20 mm) 3): 46/33/26 lines/mm.