[JSM092495]

I'm aquiring a high end 1958 Zenith, I have no clue on the condition of the tube, until I pick up the set at the end of this month, but I suspect it's weak. I need some help on some substitutions since the original tube is not common.

I have a NOS 21AMP4 or a 21ALP4, if any of those would work that'd be great. Thanks.