When the submachine guns are removed from the wine box, they are Sten Submachine guns. When they are removed from the car after the ambush they are Sten Guns. When they are finally shot at the retreating gangsters, they have become two different models of Thompson Submachine guns, an early civilian model of a Thompson and a military model (M1 or M1A1) of a Thompson.
When the trio recover Marco's body, his face is unmarked in the long shots. However, in the closer shots, he has a head wound and there are streaks of blood from the wound on his face.