Glad to see efforts are somewhat coming back for this now! Sadly, I moved and am in the south now, so my help is limited. I do have a couple 21J/F tubes that need rebuilt. One has an intermittent cathode, and the other one went purple/gone to air. There might be one or two more bad jugs sitting over there at the Boiling Springs warehouse in SC thats slowly being cleaned out. One of them was necked.

I may or may not get it rebuilt we shall see, so if not, its still a source of glass.

Colorvac in Germany, who has done other color CRT rebuilds, has restored an RCA CTC-9. The videos they had on YouTube of previous CRT rebuilds appear to have been taken down, but this appeared recently. It doesn't say whether this restoration included rebuilding the CRT, but that's a possibility:
https://www.facebook.com/share/r/1ERJSZRnKQ/