The mysterious forearm!
 

I purchased the Revoltech Ultron and was moved by a pic including a drill attachment. I obtained the drill, but it turns out I was a bit too excited and didn't look carefully enough at the original pic to notice there's more than just a drill attached the Ultron. There is a forearm piece and I can't seem to identify it for the life of me. I looked through Revoltech's catalog and am at a dead end. Any ideas?

I don't know, but that looks like some kind of home made/custom clip.