Btw, the term rounderbolt was for the thunderbolts that floated around that had a round fiberglass horn. So far we haven't found one and Federal doesn't have that documentation anymore but it was confirmed that federal experimented with it.
I don't know who did it but now people are calling the thunderbolts in the Ads rounderbolts which has blown the name out of proportion entirely.
Here's the post I heard it from 3 years ago:
https://airraidsirens.com/forums/viewto ... f=2&t=3200