Brass #6 with a lead backing?

Hi all. Sorry if not allowed. I posted this yesterday on the ‘war relic’ page. The reason I posted it there first is because a buddy of mine(not a forum sort of guy), found this in Cumberland, Md in an area where he’s recovered several three ringer bullets. I was wondering(on his behalf) if it might possibly be a CW relic. Possibly something nailed to a wagon or trunk?? Thanks ahead!