The only significant difference between the mags is that three of them have a slightly longer reinforced area (as seen in the pics)
Spoke with the old man about the mags. He said they were over stock from the old SWAT locker. They were used in a Thompson and/or GG. He's not 100% sure if they were interchangeable, but he had both weapons in the armory before they changed over to the HK MP5. I had the opportunity to shoot both of them before they got decommissioned. He snatched up a grocery bag full of mixed magazines before they got tossed in the round file. He says there were a bunch of M14, .30 Carbine, Mini14, Thompson and GG mags getting destroyed.