2014 Royal Mint Error Half Gold Sovereign

A very rare gold error  coin issued by the Royal Mint

This Sovereign in error has been minted with a different finish on each side of the coin Proof/BU 

The reverse of this coin shows an image of  St George and dragon by Benedetto Pistrucci  struck to Proof finish

The obverse, shows Her Majesty the Queen’s fourth portrait, struck to Brilliant Uncirculated finish.
This coin features the fourth portrait of Queen Elizabeth by Ian Rank-Broadley and is struck in 22 carat gold weighing in at  3.99 grams 

This sovereign is housed in its 2014 Royal Mint Box and accompanied with its COA which states the strike quality is  Brilliant Uncirculated which is incorrect hence the Mule Error