I actually submitted this. This particular piece dropped from a Skeletal Trooper (I know!) in Tox. Kinda caught me off guard cause we were focusing on Skeletal Commanders most the time.
I got these on the first or second night in Tox on the Xev server. My then 36 warrior found them very useful. I hunted in Tox for about 2 weeks after that and never saw them again. Did not hear of anyone else seeing them either.