This will ime be the circuit in the amp the OP has. https://schematicheaven.net/fenderamps/pro_5d5_schem.pdf Note the 12A-7 tubes, and remember that we can see the 12A-7s in one picture the OP gives us. As for this amp or a true 5C7 being a predecessor to the later 5E7 Bandmaster, that could be said of any of the big tweeds from 1954 on back. There was not much variation between those models but for speakers. pin fact, the 5D8 Twin is a closer relative to the 1955 and later 6L6 Fender tweeds in that it is the first to have both a treble and a bass control...with everything else being very much the same as the Contemporary Pro/Bandmaster/Super amps.