Sorry, Iam not a expert tube. TV tubes are not a problem, the 6350 is a TV tube, and had great sound, but it not a hot salles. I could not read any more than you already read.
I would be hopeful if the donor is a widow or relative, who does not know audio, but if the donor is an audiophile, the tubes should not be worth anything.
That big tubes seems to be pentodes, they had alot of pins.