Yes Lawrence is correct, I have been reading the Trader sheet 1841 for this radio. It explains that TXk2 acts as a "collector bend detector".
I have come across this circuit a couple of times and blow me I cant remember what the alternative resistor Rk4 is supposed to do. I seem to remember that it had something to do with local and distant reception, and it was mentioned in notes somewhere, that it would be fitted or not by the dealer depending on where the radio was to be used, but I cant find any reference to it now.
Could a large interference signal cause TXk1 to fail base-emitter short, if the radio was set for distant reception?
Mike