The strike type of a coin refers to the particular minting process that was used to strike a planchet into a coin. There are three basic strike types: Circulation Strike (a.k.a. Business Strike), Proof Strike and Special Mint Set (SMS). Each one of these strikes has a particular purpose that is used for within the minting processes at the United States Mint.
The circulation strike is the most common strike type used at the mint.
Remember, the primary purpose of the United States Mint is to produce coins that will circulate in commerce. For all intents and purposes, the mint facilities are factories. They take raw material (metal) and manufacture it into finished goods (coins).
The circulation strike is the most economical and efficient strike type that the mint uses. Blanks and planchets are handled in bulk bins and bags. Special attention is not given to how the raw materials are handled. The coining dies are mechanically produced while balancing quality and efficiency in order to produce the most coins at the cheapest cost.
After the coins are struck they fall into large bins for transport into the counting and bagging areas. From there they are loaded onto trucks and taken to a another facility to be packaged into smaller bags or individual coin rolls.
The proof strike is the highest quality type of strike that the mint uses.
Blanks and planchets are specially handled in order to minimize scrapes and scratches. Before they are sent to the coining press room, they are polished and washed to produce an almost mirror like surface.
The coin dies used to produce proof strike coins are also specially prepared. The devices receive a laser engraved frosting and the fields are polished to a high mirrored surface.
When the coins are struck, the coining press operator uses two or more strikes on each individual planchet to ensure the highest quality coin is produced. Each finished proof coin is removed from the coining press by the operator using cotton gloves or soft-tipped tweezers. This ensures that the coin will not be scratched or scraped until it is packaged for shipment.
Special Mint Set Strike
The special mint set strike is better quality than a circulation strike, but not the same painstakingly high quality of a proof strike. A special mint set strike usually has one or more of the following characteristics:
- Special handling of the blanks and planchets.
- Special preparation of the coining die.
- Special handling of the finished coin to minimize scratches and imperfections.
Several times during the history of the mint special mint strikes have been used. The largest quantity of special mint strikes were produced in 1965, 1966 and 1967. During this time frame the United States was experiencing a coin shortage due to the rapid increase in the price of silver. The mint was under extraordinary pressure to produce coins for circulation and did not have the time to prepare the planchets and dies for proof coins.
Therefore, they produced special mint set strike coins that were marketed to coin collectors.
The value of a coin will take into consideration the strike type that was used to mint it.