10 Zlotys Polish Team Beijing 2008

Issued to mark Poland's participation in the 2008 Beijing Summer Olympics, this coin is technically more sculpture than numismatic object — a silver ring enclosing a gold-plated duraluminium sphere that moves freely within the frame. NBP commissioned the format specifically for this series, and the kinetic insert made it one of the more mechanically unusual pieces in the bank's commemorative program. Duraluminium, an aluminum-copper alloy developed in the early twentieth century for aircraft construction, is a genuinely odd choice for a coin component — which is precisely the point.