This is a 1981 Royal Wedding Commemorative Crown Coin featuring Prince Charles and Lady Diana Spencer. 
This coin is to commemorate the marriage of Prince Charles and Lady Diana Spencer, this coin was issued by the Royal Mint in the United Kingdom.
Specifications: It is a 25 pence coin (one quarter of a pound), made of cupro-nickel, with the same diameter (38.6 mm) and weight as a modern £5 coin.