The Jupiter-12 is a copy of the wartime Carl Zeiss Jena Biogon. Early one, before 1956 or so- have German Glass. This 1952 has a Serial number stamped into the rear module that identifies it as a 1943 Zeiss Biogon. When received, the focus was off on the Leica. This is common with Russian lenses, which are made to the Zeiss standard. The shim typically has to be thickened, and this one required an extra 0.1mm. My opinion- KMZ tends to be the best of the Russian manufacturers. ZOMZ- close second. This lens, with shipping- was under $100. Puts it as the best of the bottom for Leica mount wide-angle lenses. The J-12 has a massive rear element, and will NOT fit on a Canon P or Canon 7. It fits well on the Leica M3, M8, and M9. I would NOT use it on the CL or M5. At F2.8, then F4.