Yes, it was Rexolite. I have that PDF on my machine, to explain to people about why RCA left the broadcast transmitter business. The decision to use Rexolite in the PA cavity was a really horrible decision due to how flammable that material is. And yes, those silver plated tuning and loading inductors got trashed in the worst environments and tarnished in less brutal environments. The gentleman who did that site, happens to be a really superb broadcast engineer, and designed and built a homebrew transmitter for a station.