In reference to your last picture, all t-bolt horn support bracket bolts are welded to keep them from coming loose. I had to take a grinder to mine to cut them out (as well as drill two new holes in the horn to fir my solenoid bar). I need to get pix!
I've worked on Thunderbolts from 1950s vintage to 1970s vintage and I have never seen a welded horn support. Are you saying that the support is welded to the horn to keep it from coming loose? Why would they ever put bolts in it then? Why not just weld the thing completely to the support.
Federal doesn't want to support Thunderbolts any more -- why would they be in the business of competing with themselves?
I'm still trying to figure this out. "Compete with themselves?" Huh? Federal sells parts and new sirens. How does selling parts compete with them selling new sirens? Federal is selling both things. How does one "compete" with the other? A company can only supply all the parts for a product for so long. Thunderbolts went out 20 years ago. To expect Federal to supply parts for them indefinitely is a bit ridiculous. Automotive companies don't sell parts indefinitely for all their models. They have to stock new parts for new models and phase out parts stock for old models. If Federal still stocked all the parts for Thunderbolts how many would they really sell anyway. They would have a bunch of parts stock sitting around for an occasional sale now and then. It's just doesn't make sense.