On July 22, 1942 Auto-Ordnance was awarded contract W-478-ORD-2196 to produce approximately 3,976,873 thirty-round magazines at a cost of 26 cents each. Production was to begin January 1, 1943 and be completed by September of 1943. Auto-Ordnance then subcontracted this production to United Specialty Company. USCO had also produced the Auto-Ordnance marked twenty-round box magazine.

By that time United Specialty had two plants - one in Chicago which produced 2,800,000 twenty-round magazines and the Philadelphia plant (Mitchell Division) which produced 1,185,873.

This means that for every Thompson Submachine Gun produced in the United States, there are two USCO magazines alone. It is also my opinion that the two different types of Auto-Ordnance thirty-round magazines can be traced to the two different factories as follows.

The Auto-Ordnance thirty-round magazines with the markings centered on the face of the magazines and also have the USCO marking on the inside of the backstrap were produced by Mitchell Division, Philadelphia, Pennsylvania