A couple more thoughts. While it would have been a welcome miracle if the tubes were 300A’s, any original 300B in working order will also be valuable. The engraved-base 300B’s from the 1930s can go for $20,000 a pair.
if you decide to sell the amp, you should contact Deja Vu Audio in Virginia. That is the dealer I mentioned in my post above that specializes in vintage tube amps and re-building of such amps. I have a 133 clone made by their Italian builder that is terrific sounding. It utilizes a lot of genuine parts, including the correct input and output transformers, but it is configured for stereo and has a modern power supply; the amp also runs very rare 348 and 349 tubes.