In 2009 to celebrate the 40th Anniversary of the first UK 50p Fifty Pence Coin and 250th Anniversary of Kew Gardens, the Royal Mint released a very special Limited Issue Kew Gardens Piedfort Mule Error 50p Fifty Pence Gold Proof Coin with an incorrect obverse struck in solid 22 Carat Gold Certified Slabbed and Graded by PCGS as PR70 DCAM with special NFC Anti-Counterfeiting Technology.
The Piedfort 50p Fifty Pence Coin weighs 31.10 grams and is double the thickness of its normal counterpart and has a strict mintage of only 40 worldwide and is the smallest issue ever of any United Kingdom coin.
The reverse, designed by Christopher Le Burns has chosen to feature Kew famous Chinese Pagoda while the obverse has the stunning portrait of Her Majesty Queen Elizabeth II by Ian Rank Broadley.
These legal tender coins have been struck to proof quality using specially prepared dies and highly polished blanks.
Piedforts are coins which have been especially struck on thicker than normal blanks.
As their name suggests they are closely associated with France, where from the twelfth century they were apparently issued by the Kings as presentation pieces.
In Britain, the practice of striking piedforts is later and less frequent, but medieval and Tudor examples are known.