---------- Post added at 09:49 PM ---------- Previous post was at 09:47 PM ----------
Not sure about other parts of the country, but one of the main reasons for chrome cages in the midwest was that IMCA was under pressure to legalize cages but didn't really want them so they made it as inconvenient as possible by stating that you could run a cage but it had to be chromed.
I seriously doubt that many cages in that era were treated for hydrogen embrittlement.