Here's a discussion on the antique radio forum indicating that RE does indeed mean rare earth.
https://www.antiqueradios.com/forums...1736&view=next
I have to give up my idea that you could tell the sulfide tubes by face color. The sulfide green (at times with a little cadmium to make it even yellower) had a yellowish body color, and the cadmium/sulfide red had an orange body color, making the face color quite green over all. I thought the rare earth reds had a white body color, which may be true, so perhaps the face color is mainly due to the green phosphor here (?).
Can you take a magnifying glass to the screen and see what color the dots are when off?