The reason I ask is that I have a stainless steel magazine for my 4506-1 that fits and functions fine with a thinned plastic base. With a full size base it won't insert enough to latch. An older steel 4506 base is a very tight fit. The magazine has numbered holes, and ambidextrous mag catch cutouts, but no logo. I'm guessing after-market (Pro-Mag?), but would like a second opinion.