I am new here and it seems that you have not resolved the problem.
i have not seen that you have mentioned any indication of the rated AC voltage in .. from info on the back.
normally it is near the frequency.
we need to keep in mind that the old standard was more like 110 volts and now it is often 120 volts so if a radio desighed for 110 is really getting 120 , all voltaged inside will be up by 10% .. that could be the problem/situation
i assume that you have double checked your readings with another meter?
does the radio work? does the bias on the cathode of the output tube pull the voltage on the plate down enough?
many radios have been made for 25 to 60 Hz ,using a transformer good for 25 cycles. I dont expect the rated frequency will cause your high voltages.
you did not mention where the voltages came from , but if the B+ is high , all the DC will be high.
are you using that isolation transformer putting out about 124 Volts out to feed the radio? if so you can expect some high voltages inside.