Differences in 21FBP22 CRTs

[Tomcomm]

The Greeni 21FBP22 is definitely the older (lower SN) of the two and red stamped "21FBP22" on its pin cap. Its tri-dots are two green and one bronze, the red one. RCA data sheet identifies the 21FBP22 as all sulfide. It seems the majority of 21FBP22 crts screens are green, only a few are gray. Is this your impression also?

My gray is newer (higher SN) but has no type stamped on its pin cap, only its SN. Its tri-dots are all gray. Does anyone have a verified 21FBP22A? What color is its inactive screen?

I tend to agree with Old TV Nut, my newer, unmarked gray crt may possibly be a "rare-earth" 21FBP22A?? The picture quality of both 21FBP22.. are very good, but the gray will stay mounted in the 21CT55 as I start aligning the dynamic conversion system, hope its not that painful.....Tom