Designed and manufactured by Fabbrica Nazionale d'Armi di Brescia (National Arms Factory of Brescia) in northern Italy, for use by the RSI and German military forces (as well as some partisan units). They were produced in 1943 and 1944, and only about 1,000 were made (all with serial numbers in the 5,000 range, for unknown reasons). They were quite expensive to produce, with milled receivers and a closed-bolt lever-delayed mechanism.

Interestingly, many of the surviving examples came out of Algeria, where a batch of the guns was smuggled in for use by independence forces. Their markings were milled off, and replaced by fake marks in an attempt to hide their origins - "Maschine Pistole P.M. 43" (an interesting combination of German and French elements). This example went back to France later, where it was unfortunately deactivated by the St Etienne proof house.

Many thanks to the Royal Museum of the Armed Forces and Military History in Brussels for access to this very rare piece! Check them out here:
https://www.klm-mra.be/D7t/