Nikkor-N 5cm f1.1 Rare S Mount Rangefinder Lens (read)
This is a RARE lens. I can only find a couple of mentions of it online and none for sale.
This one is in pretty good condition. The body shows moderate cosmetic wear. The focus and aperture are smooth. There are some minor cleaning marks on the rear element but otherwise the glass is clean and scratch-free with no haze nor fungus. There is a a few millimeters of what appears to be separation around the edge of the element behind the aperture.
The lens comes with the original caps.