[morzh]

Remember those two wires Kirk got zapped with?

It just dawned upon me: I think, someone was trying to make a tone control switch.

Here's the rational: both wires came from the primary of the output transformer.
I also realized the usual capacitor placed across it in Halson design is missing (of course I cannot prove it was there in the first place, but then identical Halson output solutions all have about 6nF cap across the primary).
And, although we are accustomed to see the tone control cap swutches from the anode to ground, it does not really make any difference if the switch is in between the anode and the B+, as for the AC B+ and GND are more or less the same. Which is where the primary is connected.

So maybe that what it was, that zapped Kirk.

PS. Maybe I should put a cap in parallel - it does sound a bit high-pitch to me.