This is a very late World War II production M1A1 Thompson Submachine Gun, manufactured by the Auto Ordnance Corp. in Bridgeport, Connecticut. The M1A1 was introduced in April 1942 as a war-expedient/simplified version of the M1928 Thompson Submachine Gun. The war expedient features included the elimination of the barrel cooling fins, Cutt's compensator, adjustable rear sight and removable buttstock. They also employed a side-mounted cocking handle and a fixed firing pin with a slightly longer bolt which allowed the weapon to be easier and cheaper to manufacture. This example has the standard Lyman "L" type fixed rear sight, horizontal walnut forearm and fixed walnut buttstock. The left side of the receiver is stamped with a very faint U.S. inspectors initials: "RLB" followed by a U.S. Ordnance, Cross-Cannon final acceptance proof. The left side of the receiver is marked "THOMPSON SUBMACHINE GUN/CALIBER 45 M1A1/NO. 606651" followed by "RIA/FK" indicating it was refurbished/reinspected at Rock Island Arsenal by Frank Krack. The right side is marked: "AUTO ORDNANCE CORPORATION/BRIDGEPORT CONNECTICUT U.S.A." respectively. The lower frame group is correctly marked: "AUTO/SINGLE" and "FIRE/SAFE,". This SMG comes with one 30-round stick magazine and a green canvas sling.