Royal Mint Silver Coins
The Royal Mint produce Silver Proof versions of most coins and sets for those who are looking for something a little bit special. Silver coins will usually come in a presentation box, some coins have the design detail highlighted using colour printing, the 2 sets of Beatrix Potter coins were all produced as colour on silver.
Silver coins like other metals will react to chemicals in the air and eventually start to show colour changes, even when sealed (unless in a vacuum). This change is called toning and is a natural event that can add to the appeal or look of the coin. The actual changes in terms of colours and position on the coin, combined with the collectors personal preference determine desirability and value.