Ok, i know this might seem like a stupid question, but how to i tell which gen PMAG's i own, on the bottom there is a M with an 02 under it, does that mean that they are gen 2

By looking at their web site th PMAG 30 GEN M3 has a form of stippling on the side at the bottom my Gen 2 has PMAG 30 (round number I guess as I have no low capacity mags so I don't know for sure) also has NSN-1005-01-576-5159 which could be the same for all PMAGs

Attachment 93093 Gen 2
Attachment 93094 Gen 3

This is what they look like

Why does the dust cover from a 30 round mag, fit on the bottom of the mag but not a 20 round mag? I tried the other day after seeing a few pics of people storing them there while shooting.