How can you be sure it's genuine? Coin presses are made to prevent insertion of two heads or two tails dies so it's almost a dead-cert that you have a faked magician's coin.
Drop it on a hard surface and compare the ring to that of a known good coin. The 2-header will sound dull by comparison.
Get a good magnifier and look at the edge of the coin. The seam is often concealed near one side or the other, but it'll be there.
One pound ! There were millions minted ! Every time the year changes, a new batch of coins is minted. Unless there's something 'special' about the coin (for example double-headed) - it's worth nothing more than the face value !
Therre were no 1821 British Double Sovereign or Two Pound coins minted.
There was no 1977 British One Pound coin minted. The first general circulation One Pound coins was minted in 1983.
The Pound or Sovereign was not introduced into the British system of currency until 1817 when it replaced the Guinea, and the first Two Pound coin (Double Sovereigns) was minted in 1820.
The first Eire Punt (One Pound) coin was minted in 1990, the last was minted in 2000.
There was no 1886 British Two Pound coin minted. During the reign of Queen Victoria, they were only minted in 1887 and 1893.
There were 10,191,000 60th Anniversary of the end of World War 2 British Two Pound coins minted. There were 5,140,500 400th Anniversary of the Gunpowder Plot British Two Pound coins minted.
The last British Shilling minted for general circulation was minted in 1966.
There was no 1811 British Sovereign or One Pound coin minted.
The Canadian "double-headed" cent is equal to the British One Penny. The Canadian one "cent" is equal to the British 1/2 penny (so a British penny is 2 cents or 1 double-headed cent). When first issued, the Canadian government had them struck to a standard of 100 coins to the pound of bronze rather than the the British standard of 80 coins to the pound of bronze. The first 1858 issues, however, were unpopular and originally had to be sold at a discount. It is believed the Canadians joined the two cents together to make them equivalent to the British Penny.
There were no British Two Pound coins minted from 1888 to 1892 inclusive.
The pound sterling is a coin minted by the Royal Mint. One bank in Scotland issues a One Pound note.