"This fast Nikon 1:1.2 is a fantastic lens, originally used in Nikon F mount -- was totally modified for to mount on Leica M cameras, only the optic elements was kept intact, the auto-diaphragm mechanism was disabled and now can be used as it would usually work in rangefinder lenses. It is full rangefinder coupled at all distances, the rangefinder cam will move at a calculated different rate with respect to the focusing helical to compensate the difference between 50mm and 55mm.
The new structure is CNC machined from solid brass and has a chrome finish. The front ring and the aperture ring are the original of the modified Nikon lens, this keeps the original click step mechanism and you will feel it exactly as in the original Nikon lens."