The Britannia is a British bullion gold coin issued since 1987, weighing one troy ounce and with a face value of £100. There are also fractional Britannia coins, weighing a half, quarter, and one-tenth of an ounce, with face values of 50, 25, and 10 pounds respectively. The coins have a millesimal fineness of 916 (91.6 %, 22 carat) gold, the non-gold component being copper until 1989 and silver from 1990.

In 1997 the Royal Mint started production of silver bullion coins also under the name “Britannias”. The alloy used is Britannia silver with millesimal fineness 958 (95.8 %). The silver coins are available in 1 ounce, 1/2 ounce, 1/4 ounce, and 1/10 ounce.

There has been five different sets of Silver Britannias: in 1997, 1998, 2001, 2003, and 2005.

Dimensions of Gold Britannias

One ounce: diameter 32.69 mm, gold content 31.104 g.

Half ounce: diameter 27.00 mm, gold content 15.552 g

Quarter ounce: diameter 22.00 mm, gold content 7.776 g

Tenth ounce: diameter 16.50 mm, gold content 3.110 g

Dimensions of Silver Britannias

One ounce: diameter 40 mm, Silver content 31.1 g.

Half ounce: diameter 27.00 mm, silver content 15.5 g

Quarter ounce: diameter 22.00 mm, silver content 7.7 g

Tenth ounce: diameter 16.50 mm, silver content 3.1 g

British gold coins | Coins of the United Kingdom