Yes Rick, as all of the above said:

1) Adjustable sight

2) T-3 barrel band with bayo lug

3) Four rivet HG

4) Pot belly stock can be a bonus, but whichever a good stock without a lot of wear.

5) The most important is barrel condition, whether early or newer. Measure the muzzle and check the crown.

Luckily, that later carbines are easier to find and usually less expensive. Some late ones will still be in original condition because they didn't have to go through the rebuild program. BUT, my most accurate shooter of all was a rebuilt IBM. It just felt 'solid' in it's stock and I believe it was never 'messed with' after the rebuild. (It had a mix of parts of all kinds) I don't believe it would have been so good if someone had jacked with it replacing parts, etc. like so many other carbines. You might even concentrate on finding one of the CMPicon carbines if you can find one that you're pretty sure hasn't been 'improved' recently. Maybe look for one that still has the M2 stock and FAT marking on the stock. Many people who bought the CMP carbines got rid of their FAT marked stocks before they took them to the range.

I'm with you about your quest - it would be really neat to be the only one shooting a carbine at your competitions. They aren't known to be as accurate as the others but they can be accurate out to 100 yards and you'd be proud if you beat the other guys!