all that's on the amp chassis is one 12AX7 VA / inverter.
a pair of 7025 (12ax7) per channel should be enough. That makes for a gain and an inverter stage, same as Magnavox and lots of other amps ran. Its probably about as sensitive as your typical console amp.
Looks like an earlier version of my Silvertone amp, made by Warwick Electronics branch of Thomas organ.
View attachment 578723
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Looks familiar. Hope that's still making good music for you.