Upcoming play prop "Flip Flop Circuit"

I am writing a new full length play (still untitled) and I needed a strange machine like prop that could have existed in the 1920's. I found this "flip flop" machine online that was made in 1918:

The scene is a ghost hunter who picks up strange readings and needs some kind of machine that he uses. Since the play within the play takes place in the 1920's I needed something from that time and here it is!