In the late 1940s the French developed a new suite of small arms, including a competition to replace the 7.65mm MAS-38 submachine gun with a new 9x19mm SMG. The eventual winner of this program was the MAT-49, which became an iconic part of French Army weaponry in Algeria and elsewhere. The St Etienne arsenal also submitted a design though, and theirs was a lever-delayed system. In addition to the variety of models in 9x19mm, it appears that they also made a couple examples in .45 ACP. I'm not sure why this was done, but it is interesting to see!

Many thanks to the IRCGN (Institut de Recherche Criminelle de la Gendarmerie Nationale) for allowing me access to film this prototype for you!