A member of my local club asked me about this piece. I know nothing about Chinese coins, so I told him I would ask your guys. The piece is 60 millimeters or 2 and 3/8 inches in diameter and appears to made green corroded copper. Thanks for you help!
It is genuine in the sense it is not a counterfeit of circulating coinage. Rather, these were used at burials: http://primaltrek.com/blog/2015/03/20/chinese-burial-money/. Often made out of clay, the reason for their usage instead of genuine circulating coinage was to discourage vandalism and theft from grave robbers.
That's a dragon and Phoenix amulet, with the obverse legend Zhou yuan tong bao. Not a coin, but an amulet. That legend was used on a coin during the posterior zhou dynasty, but never in that script. Looks modern, some coppery metal that was patinated.
