The British gold Sovereign was first minted in 1489. Since 1816, the sovereign weighs just under 8 grams and is .917 pure gold. The half sovereign is also .917 pure and weighs 3.99 grams.
The British Gold Britannia was introduced in 1987 and the series includes 4 coins with one ounce, one half, one quarter and one tenth ounce of gold.