If you have the chokes opened slightly, you will be fine shooting steel... I just wouldn't shoot it from the full choke barrel... you might get away with the first box, but eventually it could be costly... and on the other hand, the first shot could be costly.
Definitely going to stay away from steel. Don't plan on opening the barrels at this time. Will make it work in its original condition for now. It's in such great condition Im afraid to do anything to it haha. I also bought it off one of the eldrly gentlemen I deer hunt with so it has some sentimental value for me too owning one of his shotguns.