German MP 40/I submachine gun Serial number 9184 k (no magazine) DEACTIVATED Believed to be the one donated by John Duncan Manson. THE 1991 FIREARMS LIST STATES THAT IT WAS DEACTIVATED. Steyr Daimler Puch, A.G. Werk, Steyr, Austria, late code "bnz" believed to have been manufactured in 1942 The MP 40 was a (32 round) magazine fed which worked on a straight blowback and open bolt to fire. NOTES (WIKIPEDIA): MP 40 — main production version MP 40/I — experiment with two side by side 32-round magazines, sometimes (incorrectly) called MP 40/II.The MP 40/I was tested in 1942. This version of the MP 40 has a two-magazine receiver that slides horizontally to use the additional magazine when the first becomes depleted. This design was intended to counter the superior firepower of the Soviet PPSh-41, but made the weapon heavy and unbalanced in the field, and did not work well. However, by 1943 the Soviets shifted the production of PPSh-41 drums to 35 round magazines due to combat malfunctions. In 2001, only five genuine exemplars of the MP40/I were known to exist. The dual feed system is a feature shared with another rare weapon, the EMP 44.