I have one brown base GEC KT66. It's used but tests good. I can't use it for anything, since I don't have any single-ended amps.
Any reasonable offer and it's yours. On the one hand, it's used, but on the other hand, it's the real thing. Quad hi-fi, Clapton's Beano album, and so on. I have the box too.
Pics on request.