Euro coins edge of the €2 coin also protects it from counterfeiting. Euro coins were designed in cooperation with organisations representing blind persons, and as a result they incorporate many features allowing them to be distinguished by touch alone. In addition, their visual appearance is designed to make them easy to tell apart for persons who cannot read the inscriptions on the coins. The coins increase in size and weight with value. Of the eight denominations of euro coins, the three lowest denominations are small, resemble copper in colour and are quite thin and light. The next three denominations resemble gold in
Euro coins colour and are thicker as well as heavier. The highest two denominations are bimetallic, being generally larger and thicker than the lower denominations. In general, the greater the value, the heavier and larger the coin. Copper colour identifies low value; gold colour identifies medium value; two different metals identify high value. There are also differences within each group. The 2 cent coin has a grooved edge to distinguish it from the 1 and 5 cent coins and also from the US penny, which has the same colour and diameter. Similarly, the 20 cent coin is smooth with seven indents to