In article <4gd7gl$457@decaxp.harvard.edu>, kkobayas@scws45.harvard.edu says...

>I'm thinking about getting a used Nikon 24mm F/2.8. Does anybody know
>if the AIS and AI have same optics? I thought I heard that AI did not
>have CRC but I'm not so sure.

The 24mm f2.8 optics have not been changed since their introduction
as non-AI lenses with the knurled metal focus ring except for the
addition of multicoating many years ago. They all have
floating-element design ("CRC"), as do most Nikkor wides.
Hope This Helps