The Nippon Kogaku 2.1cm f4 Nikkor-O is clearly designed by people used to making rangefinder lenses, since it protrudes almost all the way to the film plane. Naturally, you'll need to lock up the mirror, so the whole "seeing what you're shooting" thing is out the window. Scale focusing on an SLR, of course; you may be able to fit this to a mirrorless camera adapter, but compatibility will be limited by the protruding rear element (it doesn't fit on an X mount, for example.) The upside of all this lens stuff being inside the camera is that the external portion of the lens is less than 2cm long, so if you have a compatible Nikon camera with mechanical mirror lockup, this is a pretty great little walkaround wide angle. In very good cosmetic condition, with light paint and finish wear; glass has light dust. Includes front cap, no rear cap or viewfinder.

IMPORTANT: do not use this lens on a camera that does not have a fully mechanical mirror lockup system: that means no DSLRs. This lens was designed to fit the original Nikon F, and that's still the best way to use it. We can not guarantee compatibility with adapters, so if that's your application, buy at your own risk. Please do not mess up your sensor or shutter.