“EROP” was a small company based in Paris, which produced about 18 submachine gun prototypes between 1954 and 1956. These were submitted to French military trials in several different configurations first in 1954 and later in 1956, and none of them were given any further consideration after that.
Mechanically, the EROP guns are closed-bolt and striker-fired, using modified MP40 magazines (and chambered for 9mm Parabellum). They use a small square-profile tubular receiver, and several (including this particular one) have a very perplexing buttstock system that I really can’t figure out.
Many thanks to the IRCGN (Institut de Recherche Criminelle de la Gendarmerie Nationale) for allowing me access to film this unique SMG for you!