This has been posted on the PCGS forum as well. I have not seen these before and was wondering if anyone else has. They are about 11 1/2" by 5 1/4", and weigh just under a pound each. They are metal faced and have a green plastic on the back, some with a handwritten number on the back.
That's a heavy thing to store, but whatever floats your boat I think the new home-size laser engravers can probably do this. Mostly you see products in wood, but I've been told they will make small indentations in metal.