What is this thing? The school where I teach is being remodeled (first time since 1957) and all kinds of odd things are being thrown out. The head of the science department brought me this thing because he knows I like odd things. He couldn't tell me what it was and none of our other science teachers could either. You are looking at the front side, the back side looks exactly the same except that the pointer is black, instead of red. The two things sticking up on the base are screw connectors for something, I assume wiring. This device was made by W.W. Welch of Chicago, Illinois.
If you are wondering, the thing next to it is a Union Switch & Signal Vane Line Relay for 1910's railroad signals.