I just stumbled over this Lens cap for Fisheye-Nikkor 16mm f/3.5 62K
The box is just labled wrong,,, f/2.8
Deleted link
The only listing I have ever seen for sale separately,,,
It has now been documented that I was wrong - I didn't remember what I wrote on the previous page, it is of course a mistake, and the right one is still the 64K,,,
Thank you for pointing that out.