[Dickonwheels]

The M1A1 Thompson is the early version with the cutts compensator and the finned barrel.
It also had the charging handle on top of the reciever and was the only model that could use the drum mag.

The later version of the Thompson was the M1. The action was simplafied and the charging handle was moved to the side. By the time of Normandy they had the 30 round clip As Well. From this point on they were both common and interchangable. After all a Thompson is a Thompson.

The commandos and the commonwealth forces had the M1A1.