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This set looks like it has a triode push pull output stage, typically 6AC5 power triodes were used. Since these are low gain compared to pentodes or tetrodes like 6F6 or 6V6, there are extra triode driver tubes such as 6J5's used ahead of each 6AC5. These are likely the 4 tubes at the right end, 2 drivers and 2 output triodes. Also there will be another triode phase splitter tube.
We are working on a 1941 Crosley right now which uses the triode outputs and I have a silvertone at home which uses them. I can't say the sound sounds any better than tetrodes/pentodes so am not sure why they chose the triodes but it is an interesting variation...maybe to boost up the "tube count".
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