I think that the possibility that they might be from a grave is enough to put the burden on the buyer to prove otherwise. It's known that a lot of dug artifacts such as metals are sourced from graves. Grave robbery is a despicable act, and it's not mitigated by how far down the chain you are from the actual diggers. Metals, rings and other personal items are different from issued equipment. Buying these types of personal items encourages the desecration and destruction of soldier's graves and makes the buyer a grave robbing participant.