I think I've got this right......so as I understand the issue, for anything that would be considered 'vintage', very early Nitro proofed guns, unless there are very specific 2 1/2" shells with steel shot & your bores are 1/2 choke or less, then these shells will only be loaded to conventional levels that an equivalent lead load would have (NOT high performance loads) - providing you DON'T exceed the Maximum payload if displayed on the flats like Marrakai's Jeffery 1 1/8 oz or 32g!
Otherwise use please use equivalent Bismuth shot if you're after waterfowl or game (If decreed you must in the area you are shooting in)