If Dave had been able to complete the dissection of the input module, we would have got a better view of that cam-operated rotary switch.
Those things were just brilliant, IMHO. In some cases a very long shaft off the panel knob, and extending well back into the bowels of the gear.
They had little gold-plated leaf switches soldered directly to the PC board (much like those inter-board sockets). and then a custom-molded cam on the shaft.
As you rotate the knob, various switches on the PC board would be opened or closed depending on the shape of each cam segment.
As I said IMHO, truly brilliant on SEVERAL levels. Hats off to those Tektronix designers back in that golden age.
As I drive by the Tek campus these days, it is a mere shadow of its former glory. Many of the buildings seem to be sold or leased to others.
And their custom, in-house semiconductor fab was sold to Maxim who probably still makes custom parts for Tek and others.
Here is a screen-grab from Google Maps street-view....