This amp was changed from 1x3 to all 4 tubes are finals. They are 6lb6. Changed the coax out to 316 grounded at both ends. When they changed it to all finals they removed the driver tune. You have the input match still there. It has no effect on tuning. It is a 304m with the coil soldered across the legs. One wire, off the coil, goes to the relay the other to pin #2 & 6. Pin 2 & 6 are tied together on all 4 tubes. On the other Macos i have, which are 75s, there is a resistor inline with the wire. I believe you can see the gray wire in the pic above. 238