The dual-trigger Beretta MAB 38 was an iconic submachine gun that allowed for full-auto on the back trigger and semi on the front. Larry Vickers tickles one at about 600 rounds per minute in the above short clip where you can see that the slow rate of fire and heavy weight gives a sweet ride.
Extremely well-made with a ventilated barrel and wood stock, the 9mm open-bolt Moschetto Automatico Beretta Modello 1938 and its variants were accurate and popular with those who used them, seeing lots of service not only with the Italian military but also Germany, Finland, Yugoslavia, and others, remaining in service for decades after WWII.
For a deeper dive, Ian McCollum with Forgotten Weapons goes into the gun a bit more in the below.
WW Coast Guard cutter Tampa lots of pics