They "looked" as NOS as hell. The boxes look very old but the cardboard condition is otherwise fine. The protective paper/cardboard inside looked like the valves had hardly, if ever been taken out, but they had been, as they had the seller's measurement stickers on.
Ran them in the 45/101D switch position. Filaments emit a normal glow, even with the recent rapid deterioration in sound.
Confusing. Will try them one more time, but that's twice already. Will contact the seller, see what he says.