IIRC, late(r) 1970s COLT Conversion Unit magazines should have a base like/similar to picture 1. You push in on the button until it clears the stamped metal base and slide the base off the mag. This mag has a plastic follower.
And, IIRC, the mag in picture 2 came with some of the 1st reintroduced Service Model ACE Pistols starting at Serial Number S.M. 14001 in 1978.? It should have pins and it (IIRC) was started in 1946 with the COLT Conversion Units.? (It also has a Pot Metal Base and Follower.)
Pictures 3 and 4 show the removable pin(s) in a early two-tone S.M. ACE mag.