The semi-automatic Reising Model 60 .45 ACP, shown (top) with a 12-round-capacity magazine, was intended for civilian plant guards and other security personnel. The Reising .45 ACP Model 50 Submachine Gun, shown below with a 20-round-capacity magazine, was adopted by the Marine Corps in early 1942. Photo courtesy of Smith Photographic Services, Shreveport, La.
The Model 55, made for Marine parachutists, had a wire folding stock and lacked a compensator. Photo courtesy of Smith Photographic Services, Shreveport, La.
Tangentially related, but the current Reising SMGs have the wrong mag modeled. The magazines with grooves stamped into them were single stack, and only held about 12 rounds. The 20 round magazines were double stacked and were smooth, without any grooves.
Personally I think they should make a new Paratrooper squad with the M55. Cmon. Paratroopers are a playable class now, it would only be fitting. They could make it a free event squad