Coins are small, round disks made up of either metals or alloys (in some cases even synthetic materials). They are used as a medium of exchange and are standardized in weight. They are produced in large quantities at a mint and are usually issued by a government. The first record of western coins was found in 700 BC. These coins were made from a naturally occurring alloy of gold and silver called Electrum in Western Asia Minor.King Croesus of Lydia (ruled from 560 to 546 B.C) started the bi-metallic system of pure gold and silver coins.
Most of the early coins usually carried imprints of animals such as bulls, birds or mythical creatures. Engravings of vegetables have also found to be common. The imprints were stamped on one side of the coin; tools bearing particular designs were used for the purpose.
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How Are Coins Manufactured?
Before the Industrial Age, the striking of coins was done manually. A round metal piece was placed over an anvil fitted with an imprinted die. A pestle which had another die affixed to it was then placed on top of the blank. A two-pound hammer was used to produce around seven tons of pressure on the pestle to create impressions on both sides of the metal. Heating the piece before striking helped reduce the number of strikes required.
Modern minting technique holds a high degree of mechanical and aesthetic excellence. Coins these days are manufactured under extremely strict control and tight security is provided at every stage of production. Quality checks are carried out at all stages of production to minimise loss and establish accountability.
How Are Coins Engraved?
The initial design of the coin is made by an artist in the form of a pencil sketch. Once the design has been finalized and approved, dies or moulds are prepared according to it. The detailed pattern of the selected design is made on aclay model, which is approximately three to twelve times the size of the actual coin. The completion of this process takes around 3 weeks. Plaster is then poured over the clay model to create a reverse plaster model. The words are carved into the plaster in reverse and the plaster model is perfected.
Epoxy is poured into the plaster mold to make a durable rubber mold, which is then mounted onto a transfer engraver. A stylus is used to trace the epoxy mold and a ratio bar in the middle of the engraver helps reduce the design to the actual coin size. This reduced design is engraved into a steel blank using a carbide tool. This is called a master hub, which is examined closely to get rid of imperfections. A precisely measured, heat-treatedmetal die is placed under a computerized lathe and the master hub is pressed into it. This creates a master die, which is used to make working dies.
A metal coil is fed to a blanking press to punch out round disks same as the size of the coin to be minted. These blanks are subjected to an annealing process. The misshapen and odd-sized blanks are eliminated and the perfect blanks are carried to the coining press by a conveyer belt. These are then stamped with designs and inscriptions.
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