Humans began creating coins around 700 B.C., and the process has evolved steadily since its inception. In the beginning, the manufacturing of coins was a slow and tedious task. To make each coin, scraps of metal were thinned with a hammer and anvil. Once the desired thickness was reached, the coin maker would cut each coin out from the sheet of metal and use a file and hammer to shape it.
When it was the proper weight, thickness and shape, a fixed coin die was used to strike the desired image onto the coin. The coin die, which was made from a harder metal, would then be used to imprint the image on however many coins were needed. This was accomplished by holding the die in place with one hand and hammering it into each individual coin with enough force to create the imprint with the other.
Due to the extremely manual nature of this process, coins made in this way varied widely in design and lacked consistency.
The Innovation of the Coin Press
Over the years, some improvements were made to this process. Small machines were made to hold things in place, and coin makers began utilizing weights and gravity. Known as a “monkey press,” this allowed for fewer strokes and less physical exertion on the part of the coin makers, and improved consistency somewhat.
The next big innovation in coin manufacturing was the screw press. A screw press is a simple machine press where a large screw is used to drive a ram up and down repeatedly. When used in coin manufacturing, a coin die, similar to those used in the hammer and anvil method, is placed between the ram and the coin. While the screw press was first invented and used by the Romans in the first century A.D. for wine and olive oil production, for unknown reasons, it wouldn’t be used for coin production until more than a millennium later.
In 1553, the screw press was introduced to the coin manufacturing process by Aubin Olivier. This, in addition to another machine, invented by Olivier that would punch out coins of the same size and shape, began the process of industrializing coin production.
At first though it was met with great opposition by local coin makers. It would take until the mid-1600s for the system to be adopted by first France in 1640 and then England in 1662.
Steam Power Makes an Introduction
Advances stagnated again until 1784, when a man named James Watt came up with the idea for a hammer that ran using steam, which would set coin production on a new course.
The “steam hammer” would not be built until 1840, but in realizing his idea, Watt would invent a steam condenser, which played a huge part in the industrialized minting that would soon take over coin production.
In 1788, the industrialization of coin making began when top industrialist, Matthew Boulton, used the steam condenser to invent a steam driven screw press. Installing these in his factories allowed Boulton to mint 70 to 84 coins per minute with each machine. Mass-producing coins in this manner spread rapidly throughout the 1800s, reaching the United States Mint in 1836.
Coins made during this time period became highly standardized, which made their counterfeiting incredibly difficult. Before the steam driven screw press, counterfeiting had been rampant, so many of the innovations and changes during the next century were small ones that focused on hindering counterfeit coin makers further.
Starting in the mid-1800s, a new coin press, known as the “Uhlhorn Press,” began circulating. Its inventor, the German engineer Dietrich "Diedrich" Uhlhorn, had made many advances to the efficiency of the press’s basic steam technology. By the 1940s, the new press had been sold around the world, and the screw press was gradually replaced.
Electricity and Automation
Nearing present-day, the steam press was also phased out. As society’s grasp on new energy sources progressed, the presses remained similar, but were powered by electricity rather than steam. Electric presses still remain common, though hydraulic energy is also increasingly used.
Today, most major mints use presses powered by one of those two energy sources and follow a highly-automated version of the same process used in the mid-1800s. Despite the similar process, automation has allowed coin manufacturing to happen at a much faster pace. At present, the United States Mints in Philadelphia and Denver can each produce millions of coins in a single day.
Present-day coin making can be broken down into three main steps: composition, design, and manufacturing. Each of these components is similar globally, though each country’s coinage requires its own specific mixture of metals and images imprinted on each type of coin.
The Switch from Precious Metals
Due to the high price points of gold and silver, coins intended for circulation are no longer made from those metals. Instead, gold and silver are used for commemorative and other special release coins, while standard coins are made from metals like copper, nickel and zinc.
For example, the United States Department of the Treasury reports the composition requirements for United States Mints on their website:
The “[penny is made from] … copper-plated zinc. The five-cent coin is composed of a homogeneous alloy containing 75 percent copper and 25 percent nickel. The ten-cent coin, quarter-dollar coin, half-dollar coin and one-dollar coin are all 'clad' coins, produced from three coin strips that are bonded together and rolled to the required thickness. The face of these coins is 75 percent copper and 25 percent nickel and the core, which is visible along the edges of the coins, is composed of pure copper.”
The metals required for the production of each coin are usually purchased from a commercial manufacturer.
Computers and the Pantograph
Coins are still imprinted using a single die created with the intended design, but as it is no longer a single person with a hammer in their hand; the design process is a little more complex.
Design of a coin is now done first with computer software. Once a complete digital model is created, it is developed into a plaster mold. This mold can be up to five times larger than the actual coin will be. When finished, the plaster mold is placed in another mold made of rubber resin. Melted rubber is then placed into the new mold, hardening into a silicone rubber model.
The model is then placed into a machine called a pantograph, which shrinks the model to the proper size and traces its design onto the single steel coin die. This entire process will be repeated for the design on the other side of the coin.
This die, known as the “master die”, will never be used on a single coin. Instead, multiple copies of the master die will be made to use in the striking process. The imprint on these “working dies” will wear off as time goes on, so the master die is kept to create new ones. This helps to ensure the integrity of the design and the consistency we see in modern coinage.
The design of a coin will also be required to follow certain templates, based on a variety of legal mandates and traditions that vary by government.
Coins of the United States of America
In the United States, much of the template is based on the 1792 Congressional mandate requiring that that American coinage have “an impression emblematic of Liberty, with an inscription of the word Liberty, and the year of coinage; and upon the reverse of each of the gold and silver coins shall be the representation of an eagle, with this inscription, ‘UNITED STATES OF AMERICA’. . . "
In addition to the legal requirement, coinage in the United States is produced with what is commonly called a “coin turn.” The reverse side (tails) of the coin is upside down to the obverse side (heads). Historians are unsure of where this custom came from, as it was never legislated, but the tradition continues on all circulated coins.
Another common design tradition is the existence of ridged edges on coins that were originally made of gold or silver. In the past, this was used to keep people from filing down their edges for the value of the metal. Though those circulated are no longer made from gold or silver, these edges have continued in the design of many common coins, because the ridged edge, or reeding, is useful for differentiating coins of a similar size by touch.
Completed coins are then sent out for inspection. This is usually done by a third party to ensure quality and consistency. After inspection, the coins are sent out for distribution into the banking system.
From One at a Time, to a Million in a Day
In the United States, this means that they are counted, bagged, weighed and sent to the Federal Reserve Banks. The Federal Reserve Banks then send them out until they become the coins with which we make everyday purchases. The process that ensures that those coins are of a consistent shape, weight and size has advanced from a hammer in 700 B.C. to the mass production of millions of coins per day.