Lustre

When a coin is first manufactured it is clean shiny and perfect, the word Lustre is used to describe the shininess the coin possess when new, eventually circulating coins loose their Lustre and become dull to look at, this is most noticeable in copper and bronze coins which change colour when they loose their Lustre. Below are two bronze Half Pennies the one on the right has its lustre and the second on the left dose not.