You are looking at a vintage American Flyer 709 lockout eliminator in the original envelope with instructions. it is a neat collector item from 1950-55, but of course, it has its uses as well!
The lockout eliminator allows you to utilize the dead block system with your semaphore or talking station or other accessories that stop and restart your train in a block. It keeps a very small amount of voltage going to the train to keep it from cycling to neutral so that then when the automatic semaphore (or whatever) then engages, it can proceed forward without being "stuck" in neutral.
There are some rubs, etc. to the item, and there is some dirt and minro rust underneath.