This all leather sling fits our German World War II Submachine Gun (Gun Sold Seperately) Item No. CA22-1111. The MP40 was developed in World War II and about a million MP40s were produced. The original MP40's design used stampings, and less strategically-important metals such as aluminum, but still managed to be lighter than it's predacessors because it avoided some of the heavier machined parts used in the production of the MP38.