I have a couple of questions for the experts out there. How many different varieties are there of the MR-7? Were there different stock materials? Different types of magazines (detachable "clips", hinged floorplate or blind magazines etc.)? How about available calibers? I have a real interest in picking one up for the collection but don't know very much about them and didn't see anything in the reference section concerning them. Any info or directions on where to look from you fellas would be appreciated.