I was looking at an old voltmeter I got at a decrepit yard sale, and found this underneath. It looks like a transmogrifyer control of some sort? No idea.
Radio shack tube tester?
This is not it, but there used to be a machine in the back of our local radio shack, where you could plug in any old vacuum tube, turn certain knobs and flip specific switches, and the machine would tell you if your tube needed replacement. But you had to make sure you knew what you were doing, and replace them in your TV right where you got them. Trust me on this.