As the Germans occupied the Beretta factory, I doubt this was a civilian gun, although it may have been smuggled out to guerilla fighters.
By 1944, Italy had joined the Allied cause, so I doubt that Germany was allowing the Italian military markings. These were RE for Regio Esercito (sp?); RA for Regio Aeronautica (Air Force); and RM for Regio Marina (Navy)
More likely, your gun has German Waffenampt markings that you don't recognize. Look for a sort of eagle symbol with a number. Guns destined for SS use may not have it, as they weren't part of the German army, per se.
Or, the gun may have been sold/distributed to some individual German and left unmarked.
I think you need to start with reading some basic books covering WW II guns, and the books specific to Beretta. You can also write to the Beretta factory or to Beretta, USA. The Italian embassy can surely give you the factory address. Call the info operator and ask for the 'phone number in DC. Ask for the Commercial Consul or similar title. Whoever answers will know who you need. You can also ask for or write to the Military Attache, who may forward your letter to someone in the know. Most Eyeties on embassy duty will speak English.
Lone Star