1920s Gangsters favored the drum (more ammo), while World War II marines favored the box (no bullets sloshing around on night patrol.) Because the Army (stupidly) didn't buy it early on, it got sold to a lot of other people (many State Troopers carried it from the '20s through at least the '40s, for instance), so it's a good prop to have in your toolbox if you do 20th century historical renders.