Budget grade (or just above) made in the 50s, assuming the gun is in sound mechanical condition will be safe to shoot with any modern ammo in the correct chambering (2 3/4') Shotgun ammo pressures have not significantly changed.
Shot SHELLS have gotten more efficient, the 50s saw the introduction of the plastic shot cup wad system, which meant tighter patterns.
Shot shells don't do well above 1200-1300 fps, patterns suffer. Slugs can go faster.
DO NOT SHOOT STEEL SHOT ammo in that gun!
Steel shot does not compress (squeeze down) to pass through a choke the way lead shot does. This results in excessive pressure at the choke and has damaged barrels, even split them. Not saying it WILL happen, only that it could..so avoid steel shot in that gun.
Older shotguns made before the advent of shot cups in shells generally have chokes that are "tighter" than more modern ones. Choke was determined by the percentage of pellets inside a 30 inch circle at 40 yds. The old card wad shells without shot cups always had some pellets in contact with the barrel on their way out, which flattened one side so they didn't fly "true". Old chokes were tighter (smaller diameter) than current ones to account for the percentage of pellets that were going to go "off: from the shot column in flight. Those chokes absolutely should never have steel shot put through them.
Personally, I'd be fine with that gun, shooting 3, 3 1/4, or 3 3/4 dr eq loads. I would avoid regular use of "baby magnum" 2 3/4" shells, simply to avoid extra stress.