http://www.ebay.com/itm/Rare-Vintage-Boardwalk-Hall-31Atlantic-City-Halloween-Casino-Chip-2-50-Shipping-/222003084409?hash=item33b06a3c79:g:mUAAAOSwpRRWovgn

This was a privately issued souvenir chip issued in connection with a Phish Halloween 2010 concert held at Boardwalk (convention) Hall. Illustrated in "Black's Catalog" under Potpourri. Not a "casino chip" and certainly not a $31 one.