Doubled Die Errors: Some state quarters exhibit doubled die errors, where the design elements appear doubled. These errors occur during the minting process and can make the quarters highly valuable to collectors.
Off-Center Strikes: Quarters that were struck off-center during the minting process are considered rare and can fetch a premium. The off-center strike creates a unique visual effect, making these quarters collectible.
Missing Clad Layer: State quarters that have missing or incomplete clad layers—resulting in a partial or full exposure of the underlying copper core—are rare and valuable due to the minting defect.
Wrong Planchet Errors: Quarters minted on incorrect planchets, such as those intended for other denominations, are considered premium errors. These coins often have unusual weights or sizes compared to standard quarters.
Silver State Quarters: Some state quarters were issued in silver as part of special collector sets. These silver quarters are worth more than their copper-nickel counterparts, particularly in uncirculated condition.
Inverted Die Errors: An inverted die error occurs when the die is mistakenly positioned upside down, leading to an unusual appearance on the coin. These are rare and highly sought after by collectors.
Die Crack Errors: Quarters with die cracks—visible lines or cracks on the coin's surface due to die wear or damage—are considered premium errors. The unique appearance of these cracks can add significant value to the coin.