Here's a tough question...why would an ironhead have three voltage regulators?

The Cycle Electric on the genny is a solid state and "should" be fine and working unless someone fried it but that would be tough. Not impossible mind you, but tough. The small chrome one looks to be mechanical and if it is then it probably went bad and was just left on the bike. Ironheads are known to shake and the parts inside those things are fragile. The one on the far side looks to be mechanical as well but it's hard to see. Maybe some better pics of what you have, even if they are not mounted that's ok.

IMO, the CE reg on the genny is the one to keep or replace. The others are just junk.