There are four main types of errors on coins.
1) Off-Center: An off-center error occurs when the dies used to strike the coins don’t apply equal force on both sides, resulting in one side of the coin being more prevalent than the other. This type of error can also occur when the dies are not properly aligned in the coining press.
2) Strike Errors: A strike error occurs in the coining process when the dies that create the coin design don’t strike the blank planchet properly. These errors can range from weakly struck coins, to broadstrike errors, to double-struck errors.
3) Die Cracks and Breaks: A die crack occurs when a die cracks, causing part of the design to be missing or distorted. A die break occurs when a part of the die actually breaks off. This type of error often results in a jagged or broken design element.
4) Grease Errors: Grease errors, or greasy coins, occur when oil or grease gets onto the die before it strikes the coin. These errors create a raised area on the coin that resembles the shape of whatever caused the grease to be on the die.
These types of errors can vary in rarity and value, so if you believe you have a rare error on your coin, it’s best to take it to a professional coin dealer or numismatist for more information.
For more information on errors on coins, here is a helpful video: https://www.youtube.com/watch?v=e9XUzd6FJWE
