The Spanish-made MP41/44 is a licensed copy of the Erma EMP submachine gun. The development begins with Heinrich Vollmer in 1925, designing a submachine gun for German military testing. The military trials showed a number of flaws in the gun, and Vollmer updated the design to fix them - but by the time he had it perfected his main source of funding (the German government) dried up because of the Great Depression. Vollmer had not been able to get a substantial contract for his guns, so he sold the rights to the design to the Erma company in 1930. Erma was able to market the guns much more widely and effectively, and was able to sell more than 20,000 of them worldwide.
Mechanically, the EMP is not a strict copy of any other guns that were then on the market. It used a double-feed magazine (unlike the Schmeisser-designed guns like the MP18 and MP28), a pretty typical open bolt blowback operating mechanism, and a simple disassembly system which would be copied in principle for the MP38 and MP40 submachine guns.
The Spanish use of the EMP dates back to the Spanish Civil War, when both the Republican and Nationalist forces purchased them.The design was well enough liked that after Franco's victory, the La Coruna arsenal arranged a license to produce them in 9mm Largo for Spanish military use. This was designated the MP41/44, and that's what we are looking at today. The main mechanical difference between the Spanish and German guns is a plunger type safety located between the trigger guard and front grip.
Cool Forgotten Weapons merch! http://shop.bbtv.com/collections/forgotten-weapons