Human civilizations have long used metals as a medium for exchange. In addition to their long-lasting properties, metals lend themselves easily to melting and casting. As early as 1000 B.C. , the Chinese were using a type of metal token to represent payment. These artifacts have been labeled "spade" and "key" money because of their resemblance to a digging tool and to the modern-day Yale key. Both types bore denominations and were cast from molds. Although the ancient Egyptians did not mint coins, gold weights and rings were used to trade for products and services.
The first record of Western coins did not occur until 700 B.C. , in western Asia Minor. Evidence of coins made from a naturally occurring alloy of gold and silver called electrum were found in the foundation of the temple to Artemis at Ephesus on the banks of the Aegean Sea. King Croesus of Lydia, who ruled from 560 to 546 B.C. , has been credited with creating a bi-metallic system of pure gold and pure silver coins. These early coins typically carried imprints of animals, such as bulls, birds, insects, or mythical creatures. Engravings of vegetables were also popular. Imprints were stamped on one side of the coins with a tool bearing that particular design. Coin design was elevated to an art form during this period, and elaborately imprinted coins were afforded a high status. Many Greek cities vied for the distinction of having the most beautifully designed coins.
Alexander the Great built mints throughout his kingdom, from Macedonia to Babylon. He instituted uniform weights and types. It was during Alexander's reign that the coin portrait rose to popularity. Rulers, gods, and goddesses were the portraits of choice. By the fourth and fifth centuries A.D. , engravers in Italy, and particularly in Sicily, were generally recognized as the experts in coin design. So revered was their skill that the engravers began signing their work.
Before the advent of the Industrial Age, the striking of coins was accomplished manually. A round blank of metal was placed over an anvil that had been fitted with an imprinted die. Another die was affixed to a pestle, which was then placed on top of the blank. The coin maker held the pestle in place with one hand and then brought a two-pound hammer down on top of the pestle. Remarkably, this resulted in seven tons of pressure, which forced impressions into both sides of the blank. The high relief typical of early Greek coins sometimes required two or three blows to achieve the desired effect. Heating the blank before striking often reduced the number of required strikes. This method allowed one coin to be struck every two seconds.
Each country institutes strict guidelines for the composition of its currency. The outside vendors who provide the metal or "stock" to the mint must follow these guidelines to the letter. Originally, the U.S. penny (or cent) was composed of 95% copper and 5% zinc. In 1982, this composition was changed to a copper-plated zinc. A zinc alloy with traces of copper constitute the core of the coin, while the outer surface is electroplated with copper. Five-cent coins are composed of cupronickel, an alloy of
In the factories of the outside vendors, the metal alloys are melted in furnaces and poured into rectangular molds. When the stock cools, it is rolled under pressure to the appropriate thicknesses. The rolling process causes the stock to harden excessively, requiring the application of a process called annealing. In this process, a series of heatings and coolings softens the stock and brings it to the consistency needed for shaping and stamping. The rectangular sheets of metal are cut into strips approximately 13 inches (33 cm) wide and 1,500 feet (457 m) long, and then rolled into coils. The mints purchase the coils according to their needs.
In some instances, the collar has grooves to make the ridged edges on the coin. Otherwise, the grooves are made after the striking process, on a tool called an upsetting mill. The size of the press varies from single capacity to ones that stamp four coins simultaneously. Single-striking presses generally stamp 400 coins per minute, with pressure loads up to 180 tons. Multiple presses can crank out 120 coins per minute under 250 tons of pressure.
Inspections are carried out at many points throughout the engraving and manufacturing process. Alloys are analyzed using xray fluorescent spectrometers or chemical processes. The surface condition of the blanks is checked frequently for maximum center line average. The diameters of the blanks are measured with gauges such as micrometers. Weights are controlled by weighing a specific number of coins against a standard weight plus a pre-determined allowance.
In the mid-1990s, the U.S. made preparations to join other industrialized countries in the use of a dollar coin instead of a paper bill. Although backers point to the savings that the switch would bring, and environmentalists extol the virtues of phasing out the dollar bill, traditionalists see the dollar bill as a well-entrenched symbol of the United States. Unions and trade associations representing the paper industry also voiced opposition to the new coin.
Elimination of the penny has also gained support in recent years. Ironically, the American public's view of the penny as worthless has caused millions of people to stockpile them in jars and boxes at home, to be traded in for larger denominations at a later date. This has led to a shortage of pennies in the commercial arena. Decisions about eliminating coins are intensely political, attesting to the continuing symbolic power of the metallic coin.
"The Art of Money." The Economist, January 15, 1994, p. 91+.
Georges, Christopher. "House Republicans, Believing Change is Due, Consider Plan to Insert Coin in Place of $1 Bill." The Wall Street Journal, April 18, 1995, p. A22.
"Noncents." The New Republic, August 8, 1994, p. 7+.
How Coins Are Designed and Produced. The Department of the Treasury, United States Mint, Philadelphia, Pennsylvania, June 1992.
U.S. Mint: Its History and Coinage. The Department of the Treasury, United States Mint, Philadelphia, Pennsylvania.
— Mary F. McNulty