Initially, the coins were 91.67% pure gold, alloyed with copper (and later silver from 1990) to improve durability.
Since 2021, the coin has integrated four advanced security features, including micro-text and a latent image that changes from a padlock to a trident as the coin is tilted. The "Tax-Free" Legend buy gold britannias
To meet global demand for higher fineness, The Royal Mint shifted to .9999 (24-karat) pure gold. Initially, the coins were 91