I have a NOS Channel Master Rebuilt 21Fwhatever22 from 1980 (Terry, you have the box for it)
I don't think Challenger is associated with them, sounds like an independent brand.
My 7 has the 21CYP22 but I don't know if it's an "A" or not?
And since it barely has a picture, much less color, I don't know what it looks like
