I was just trying to figure this one out last night... Although there is no clear cut way to find out... the easiest way is

for 28mm

1)... if it has 2 two sets of aperture numbers one small one big.. then it either it is AI or was a non-AI and has been factory AI-d (automatic indexing).
2) not all 28mm have CRC... my lens is an AI and is does not have CRC... it does focus to 1ft.. according to MIR it does NOT have CRC, but it is pretty sharp (i'm using it on digital though, dx and haven't seen corners on film)
3) from what i found the AI-s (or AI-S) version does have CRC...
4) The way you can tell it is AI-S, is it has a half-round cut on the bayonet mount... < MOST LIKELY TO HELP YOU FIGURE THIS ONE OUT, after this is autofocus.

stay away form series e... maybe my copy, but the 28mm really sucks (plain and simple), and does not have crc.

kenny seems to have the best info on this or at least the most outright


according to mir... AI, no where on the page for 28mm does it mention CRC, then came series e, then AI-s with first introduction of CRC