This is an Eastern Electronic magneto synchronizer. It is used to time the aircraft magnetos to the engine, as well as to set the internal timing of a magneto. When the points open, the lights come on. I have photographed it with the power switch turned on so you can see that the lights work. The buzzer works too of course. I have two of these, and only need one, so this one is up for grabs. If you search the web, you will see that these things sell for $90.00 - $100.00. You can save a few bucks by buying this one. If you are an A&P you need one of these things. Maybe you are an aircraft owner and want to check your own mag timing. It's not rocket science, but you need a mag timer to do it.
I only accept pay pal and will only ship to the USA. Please don't bid if you have something else in mind.
Good luck and thanks for looking.