Coin weights were made to correspond to the weights of particular coin denominations. They were most commonly made of brass or other copper alloy and were generally produced for high-value coins made of gold rather than silver. Their purpose was to check the weight of coin in circulation and ensure that coin received was of good quality. Normally they would correspond to the lowest weight at which the coin remained legal tender. They could be used to guard against clipped, worn or counterfeit coins and to check the standards of foreign coinage permitted in currency. Coin-weights or 'penny-poises' are mentioned in Statutes as early as 1205 during the reign of King John for use as a deterrent against the passing of light or clipped coins. No official coin-weights are known for the silver sterling penny and in fact all known coin-weights of English origin are for gold coins until the reign of Charles I (1625-49). The first weights that we recognise from documentary sources today are those for the gold Noble and its half and quarter dating from the 1420's. Early English coin-weights are round and uniface, and the design is usually based on the main design of the coin that it represents. From the beginning of the 16th century square coin-weights were used, still uniface until Henry VIII's reign, when the coin value in shillings (S) and pence (D) began to be placed on the reverse in Roman numerals.