just picked up this beautiful, old 22 has a really unique action with a dissassembly/take down feature where you push in on an exposed large round faced pin on the back of the receiver. it slides over, then all the "stuff" slides out the back of the receiver tube. It was supposedly made by marlin long ago possibly a mod 50 or 50e semi auto. is anyone familiar with this? what is it's marlin equivalent, where can i get the magazines?