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This is a Zastava M84, a licensed clone of the Czechoslovakian Vz.61 machinepistol.
Quite simple, .32 Auto (often called 7.65mm Browning in Europe), straight blowback, fires from a closed bolt, and feeds from 10rd and 20rd detachable magazines. It's a very compact automatic weapon, meant to be the size of about a large service pistol.
It's easy to carry on your hip and is unobtrusive.
.32 Auto isn't the most potent pistol cartridge, but together with the Skorpion's rate of fire reducer, it makes this a very easy weapon to control, even with the stock folded up and shooting with one hand, this gun barely rises on you, it's easy to put a good and solid salvo on target at close range, and even easier with the stock and a two hand grip. With armor piercing ammunition (however little armor this might pierce), it would probably be decent.
Mainly this kind of gun was intended as a defensive weapon for armored vehicle crew, say your tank or armored carrier took a bad hit and you need to bail to not be cooked alive, this kind of weapon would offer better defensive capabilities than just a normal pistol.
It would be carried with a 10rd magazine so it's easy to fit and pull from the holster, then your spare magazines are 20rd.