I'm in the process of picking up another TC, 1975 production. This one has a cotter pin holding the selector screw in place. Looking at it, it appears as though there should be a small spring that pushes out on 2 little BBs, which in turn snap into small recesses on the sides of the hammer. So, it should click when you turn it, I guess.
If that's right, where can I get those little parts?