The first coins were developed independently in Iron Age Anatolia and Archaic Greece, India and China around the 7th and 6th centuries BCE. Coins spread rapidly in the 6th and 5th centuries BCE, throughout Greece and Persia, and further to the Balkans.
Numerous coins have milled or reeded edges, initially developed to make it much easier to identify clipping. Circulating coins commonly experienced "shaving" or "clipping". The general public would cut off small quantities of valuable metal from their edges to sell it and then pass on the mutilated coins at amount. Unmilled British sterling silver coins were often decreased to almost half their minted weight. This kind of debasement in Tudor England was talked about by Sir Thomas Gresham, whose name was later on connected to Gresham's law. The monarch would have to periodically recall coins, paying only the bullion value of the silver, and reminting them. This, likewise called recoinage, is a long and tough procedure that was done only occasionally.
The side of a coin carrying an image of a king or other authority, or a national emblem, is generally called the obverse, or informally, heads. The opposite, which might hold the denomination, is typically called the reverse, or tails.
Bimetallic coins are in some cases used for greater values and for commemorative functions. In the 1990s, France utilized a tri-metallic coin. Common flowing bimetallic examples include the EUR1, EUR2, British ₤1 and ₤2, and Canadian $2 and a number of Peso coins in Mexico.