These coins have been hitting the market for a while now, and it really isn't understood what they actually are.  They are one-sided coins, and noticeably thicker.  The edges are smooth all the way around.  It would seem that the only coins found this way also coincide with the POTF2 Millennium Minted Coin series, and most people believe these are prototypes for that series.  I'm still unconvinced though, although when it comes to coins, wonders never cease.