Do commemorative coins tarnish over time?
With time, all coins show signs of ageing. Various terms are used to describe this process such as tarnishing, discolouring and toning. It is a natural process, although the speed at which it progresses depends largely on the environment in which the coins are kept. In most instances, it is a very slow process and the natural patina which develops is considered by many to enhance the beauty of the coins.
The tarnish on a coin is made up of the product of the corrosive element in the atmosphere and the metal from the coin surface. If the tarnish were to be removed, the coin surface might become pitted and very unattractive after cleaning - therefore we do not recommend cleaning.
Obviously, over the years The Royal Mint has continually improved the production process for proof coins and therefore, our more recent products are less likely to tarnish. However that is not to say that the newer products will not tarnish; as indicated, this is a natural process.