The Reising submachine gun was designed by American Eugene Reising and patented in 1940. Production of the new submachine gun commenced in 1941 at Harrington & Richardson (H&R) arms factory. In 1942, US Marine Corps signed first contract for delivery of Reising M50 submachine guns, and several tents of thousands of Reising M50 SMG's were delivered to USMC during the war. It must be noted that USMC weapons were slightly different in appearance from original version, having different trigger guard, larger takedown screw head, and other minor changes. Similar weapons were sold to various US agencies to guard military facilities and other important locations in USA. For USMC paratroopers and tankers H&R produced a folding-stock version, known as Reising M55. H&R also produced a semi-automatic only version of the M50, known as M60, which was used for training and guard purposes. The least known version is the Reising M65, a training semi-automatic weapon chambered for .22LR ammunition. It must be noted that US Marines generally disliked the Reising gun for its poor reliability, especially when gun was fouled or dirty. However, it was quite accurate and sufficiently reliable in 'urban' conditions, so many Reising submachine guns were used by various US Police departments through several post-war decades.