You really need to be careful with those old two and three piece rims. I've seen holes in a 3/4" thick plywood wall where one of those rings blew off and went through the wall!
The tire had been mounted sometime before and was sitting in a rack!
If you plan on using them, inspect the rings and rim for cracks and rusted portions
REAL GOOD. I would sandblast or wire brush them to get them down to bare metal so you can see real good any defects. If you find any defects, throw them in the scrap pile, it's not worth it to endanger your life or anybody else's life.
When you mount the tire/tube on the wheel, take a chain and wrap it around and through the wheel/tire assembly
before you ever put any air in. Allow only enough slack to get the chain off after you inflate the tire. Big tire stores and truck stops have a steel cage they use to air tires up in, and some use a chain, too. It's best to use a clip on air chuck so that you don't have to have your arm over the wheel. Add air slowly, watching and listening. Act like your woking with a bomb, because you are! After you get it aired up, let it sit a few minutes, then bump the ring with the sledge hammer.....don't take that chain off before you do this! If everything stays put, it's probably OK.
I know this may sound like a bunch of malarky, but there was a reason they outlawed 3 piece rims, and changed the design of 2 piece rims.
THEY CAN HURT OR KILL YOU!!!!!
Use this information at your own risk.