Coin currency is money made of metal, typically gold or silver. It is used in most modern economies as a medium of exchange, although paper money is also used. Most coins show the image of a monarch or other authority, and may also include other information such as the date of minting. The side showing the monarch or other authority is called the obverse; the other, which often shows a national emblem or similar symbol, is called the reverse. The space between the obverse and the edge of a coin is called the exergue; it may be blank or contain a privy mark, or may otherwise add to the aesthetics or value of a coin.
The first coins were made of precious metals, but later other materials such as copper were used. The modern quarter, for example, is worth 25 cents and is made of a cupronickel blend (copper and nickel). It has George Washington on the front and a United States emblem or design on the back. The quarter is widely accepted as a means of payment for various goods and services such as laundry, vending machines, airport trolleys, parking meters, etc.
In antiquity, a variety of primitive currencies existed that were not necessarily monetary, and some survived until historical times. For instance, the iron ingots known as talents, found among hoards of Argos and other Greek cities of the 7th century bc, probably acted as a medium of exchange, though it is unclear whether they were valued for their weight or for their metal content. Small bronze celts (prehistoric tools resembling chisels) found in hoards in Western Europe and elsewhere also likely served a monetary function, as did the small iron rings, sometimes impressed with an inscription, known as fishhook currency.
The development of coinage in the ancient world coincided with the rise of international trade and political power, and reflected the growing need for a medium of exchange that was reliable and portable. By the middle of the 6th century bc, coinage had spread from Corinth with its consistent obverse type of a pegasus to most of Greece and also to Magna Graecia, Sicily, and the Dorian colonies.
Throughout the world, countries produce circulating coins to use in everyday transactions. Some of these are minted for commemorative purposes, to honor an event or person. Cryptocurrencies such as Bitcoin have grown from digital novelties into trillion-dollar technologies that are used for a wide range of purposes. These innovations are transforming the financial industry, and many governments are seeking to regulate them.
Congress, the only federal agency with the exclusive power to coin money, passed its first Coinage Act in 1792. The act established the U.S. Mint in Philadelphia to produce circulating coins for the nation. Today, the Mint produces a variety of circulating coins in denominations from one cent to a dollar, as well as Commemorative Coin programs to honor people, places, and events.