During World War Two, Madsen (DISA) manufactured a licensed copy of the Finnish Suomi (see: https://youtu.be/hjs1uiAIpNQ). When the war ended, they wanted to replace this with a more modern, inexpensive design of their own. The result was the Model 1946 Madsen, a creative clamshell design of stamped parts. It is a very simple blowback, open-bolt 9x19mm SMG that perfectly fit the post-war era. The M46 version was sold to a few countries, and after some continued development and refinement the M50 version was demonstrated to a public audience in November 1950. This pattern was even simpler than before, and proved a popular gun for many unaligned countries in Central and South America and Southeast Asia - so much so that it remained in production until the 1980s. A bunch were imported into the US in the 1950s and 1960s, and they found a home in the movie industry, where they were often used in fantasy/sci-fi films to avoid having guns that would be recognized by American movie audiences.