The 20 pence coin was first released on June 9, 1982, according to the Royal Mint. Approximately 66 million have been minted and are in existence, as of 2014.
The Royal Mint also states that the 20 pence coin is comprised of 84 percent copper and 16 percent nickel. It measures just less than 1 inch wide and weighs 0.18 ounces. It is a seven-sided coin, is 1/16 of an inch thick and can be used for purchases up to 10 pounds. It was made to help reduce the weight of coins in the pocket and was meant to reduce the number of 10 pence coins held.