There are approximately $8 billion worth of coins circulating in the U.S. today. In the past 30 years, the U.S. Mint, who is responsible for designing and producing the nation's coins, has minted over 300 billion coins, worth about $15 billion!
Since its creation in 1972, the U.S. Mint has grown into a large enterprise with more than $1 billion in annual revenues and 2,200 employees. It is by far the world's largest manufacturer of coins and medals, producing coins not only for the U.S. but on behalf of several other countries as well.
It can be interesting to know how coins are minted. In order to make coins, the U.S. Mint purchases strips of metal (rolled into coins) in the proper dimension and thickness.
Zinc metal strips coated with copper plating are used to make pennies. Strips used for nickels are comprised of a 75% copper, 25% nickel metal alloy. Dimes, quarters, half-dollars and dollar coin are produced of strips consisting of three metallic layers fused together. The outer layer of these strips are comprised of the same alloy as that used for nickels with the third (core) layer being comprised of copper.
The first step in the coin making process involves the feeding of the metal strips through what is know as a "blanking" press. This press punches out cut round disc (blanks) about the same size as the finished coin. These blanks are then heated in a furnace to soften them. Subsequently, the softened blanks are placed rotating barrels of chemical solutions to clean and polish the metal. The cleaned and shiny blanks are then washed and dried.
Next, the blanks are sorted to remove any defective ones and the rest are put through as " upsetting" mill which raises a rim around the edges. The rimmed blanks then go to the coining or stamping press where upper and lower dies stamp the designs and inscriptions on both sides of the coin simultaneously. At this point, the blanks become genuine U.S. coins.
Finally, the finished coins are mechanically counted and placed into large canvas bags for shipment to the Federal Reserved Banks. From there they are shipped to local banks on an as-needed basis.
When the U.S. Mint was established the law required that all coins be made of gold, silver or copper. For a considerable period of time afterwards, gold was used in the $10, $5 and $2.50 pieces, silver was used to make the dollar, half-dollar, quarter, dime and half-dime while the penny and half-cent coins were made of copper.
In 1933, during the Great Depression, the U.S. Mint stopped making gold altogether. In 1965, as a result of a severe silver shortage, Congress dictated that silver no longer be used in kaming quarters and dimes. In addition, the silver content of the dollar (previously 90%) was reduced to 40% in 1965 and then eliminated entirely in 1971.