Ed got it first - It is a Contact Tool sometimes called a contact burnisher

The Nike-Hercules system had a lot relays that were used to make or break circuits. The relays were operated by coils and they had contacts much like an old telegrapher's Morse code key. After much operation there was a carbon build-up on the contacts.

The next to last picture above shows a very thin metal leaf covered in diamond dust. You stuck that between the contacts, then held the contacts gently closed, and moved the metal leaf back and forth.

There were also interlocks on most of the doors that disabled everything for safety if the door was opened. It saved the curious from electrocution. Those interlock contacts had to be cleaned occasionally.