This is an early 1960s Nikon Nippon Kogaku Nikkor 2.8cm f3.5 Non-AI lens which was developed for the Nikon F.  Nikon F lenses were only marked in cm (as opposed to the current mm) for just over 3 years.  From approximately 1963 to the present day Nikkors with this focal length have been marked as 28mm lenses.  This makes these early lenses doubly desirable for owners of Nikon Fs, as the cm designation not only makes them rare, it is also a link with a tradition stretching back through 1950s rangefinder cameras, to the first 35mm lenses produced between the wars.  The lens is also marked 'Nippon Kogaku' (the company name), a practice which stopped around 1966.

The lens is optically mint, with no visible scratches on the front and rear elements and no visible internal dust.  The focus is smooth and the aperture is oil free and snappy.  Cosmetically the only significant sign of use is slight paint wear on the focus ring (See the photos).  It would be an ideal partner for an Excellent ++ or Mint- Nikon F.  As shown in the last photo, it comes with a red velvet lined leather case which has the 'Nippon Kogaku - Tokyo' logo impressed on the lid.

Please see my other listings for additional Nikon F items, including a 13.5cm lens.