The Gold Britannia

Issued since 1987, the British Britannia gold bullion coin are offered in four denominations: one troy ounce (face value £100), half troy ounce (face value £50), quarter troy ounce (face value £25) and one-tenth troy ounce (face value £10). The Britannia coins have a purity of 22 karats (.917 millesimal fineness), the non gold component is currently silver, copper used to be the non gold component before 1990.
The one troy ounce uncirculated coins are offered at a premium of 3% to bullion dealers and therefore after distribution cost, buyers would expect to pay about 5% to 10% premium on top of the gold prices for the coin. Fractional size coins (less than one troy ounce) usually demands a higher premium of about 10% to 15% for the half and quarter ounce and as high as 50% for the one-tenth per ounce, this is because the Britannia coins are offered with a higher premium to bullion houses.