Here is a Power Shield Auto Reverser and Circuit Board that came off of a working layout. As you can see, it is mounted on a piece of wood and has some wires attached.
This was put out many years ago by Tony's Train Exchange. I do not think they produce them any longer. It was on a large G scale layout with NCE DCC.
CONDITION: C-6. Came off of a working layout. Appears in good condition.