Nikkor 2.1cm f/4 O non-AI ('59 - '67, this sample circa '65)
Filter size: 52mm
Close focus distance: 3 feet, 0.9 meters
Aperture range: f/4 - f/16
Aperture blades: 7
Depth of field scale for f/4, f/8, f/11, f/16, and IR focusing index.
Design: 8 elements in 4 groups
Nikkor Thousand and One Nights
This is an interesting and rare lens (about 6000 made in total). It basically can only be used with the F and the F2: because it is intrusive you need full time mirror lock up, and the body needs a tab to index the focus helicoil. Some of the later versions (serial number after 225001) can be used on some Nikkormats as well. The lens should be focused at infinity for mounting and dismounting. The focus indexing mark ends up angled off near the index mark for the F-mount, which is strange.
Performance is pretty good. Depth of field is huge so guessing the focus distance works well. The close focus is lacking, but understandable since parallax becomes an issue.
Mine came with a broken back cap. With help from Bill Moretz from ProCamera, I made a custom back cap from a Nikon back cap and a film canister. Just use the appropriate-sized hole saw to cut a hole in the back cap, slip the film canister through, and seal it with silicon RTV.
Mine didn't come with a finder either, so I got a Voigtlander 21mm / 25mm brightline finder (which is probably a lot better than the original, expensive, and collectable Nikon finder). You may also need an adapter with the F or the F2 since they lack cold shoes.
More photos from this lens