I got a pair of them in a shelter I bought from the junkyard. I hadn't paid too much attention to them when I had initially looked inside the shelter (which had a lot of shelving and junk in it) but did wonder why a couple of the shelves were brown.
When I got it home I looked them over and saw there were actually two ID panels, and two brackets that they slide into.
In case anyone gets worried, the military do not consider these to be secret or sensitive items, so we're not giving anything away here.
Cheers