That is an odd layout*, is the schematic online somewhere? Since this is older gear, it is probably a 6.3V transformer, 6.3 and 12.6 volt transformers were som

That is an odd layout*, is the schematic online somewhere? Since this is older gear, it is probably a 6.3V transformer, 6.3 and 12.6 volt transformers were some of the most common and cheapest voltages before the rise of cheap switcher supplies. 6.3 and 12.6 were the optimum voltages for powering the filaments of vacuum tubes and became standard voltages in transistor gear since they were cheap and available, even today transformers in these voltages are easy to find cheaply on the surplus market. *Edit: Nevermind, I read that as you had 120 and 220VAC transformers followed by a 6.3VAC transformer, you have one transformer with 120/220 primaries and a 6.3VAC secondary. Not odd at all.