I bought this heap of magazines for a multi-target competition. For which they will be altered to take max. 10 rounds.

Observed stamps are:
AI (lined above and below), BW, G-B, G-Q, IA, IS, IU, IW (in circle), M, MN, R-Q, (SP), SY-B, UQ, UU, O SG, 01 B

So, before I get to work, are any of these so rare that I should avoid irreversible alterations, bearing in mind that these are all well-used mags, not showpieces?