I got this today at work. I found this in eBay. https://www.ebay.com/itm/super-rare...860086?hash=item3d8ecdd8b6:g:rCkAAOSwyNtdH8BL
That is part of a teller's stamp that was on the strap of bills. Not an error. If someone is stupid enough to believe that it is an error, they deserve to lose $900 IMO.