In 1997 the UK Mint started issuing every year a one ounce silver coin called the Britannia.
These coins were made of an alloy comprising 95.83% silver by weight with usually copper added.
The actual weight of these Britannias was higher to ensure the coin contained 1 Troy ounce of fine silver.
This alloy was known as 958 silver which was different to sterling silver which is 92.5% silver and 7.5% base metals.
In 2013 the Mint decided to issue Britannia's in fine silver possibly to be more in line with other International mints.
The first batches of coins were a disaster for the reputation of the Royal Mint as the faces of the coins were badly scuffed and scratched through their production processes having not taken into account the much softer silver compared to 958 silver.
More recent Britannia's whilst still minted in fine silver no longer have highly polished surfaces and have migrated to structured surfaces that do not show up scratches so readily.