Released in 2017 by the Royal Mint to commemorate the Platinum Wedding Anniversary (70 Years) of Queen Elizabeth II and Prince Philip. 
 
Please note the slightly different Obverse with Prince Philip (as per photos)
 
*Not released into general circulation*
 
Obverse: Queen Elizabeth II and Prince Philip, Duke of Edinburgh on horseback, legend and dates around. (see photo)
Reverse: Conjoined portrait depicting Queen Elizabeth II and Prince Philip, Duke of Edinburgh right, legend around.