Greetings,
I have a plastic tub full of Berdon roughed out shell plates.
Yes, they appear to be mild steel, as analyzed via XRF scanner.
The center holes (1 1/4") are much larger than the Star.
Also, double check the hole indexing of the plates. The Star plates are not indexed 30 degrees to the shell slots.
Berdon made some interesting stuff. He was local and I saw him at the Goon Shows.
Cheers,
Dave