Based on professional numismatic knowledge, numerous types of errors can be found on U.S. nickels, often making them valuable to collectors. While the provided context titles indicate that comprehensive lists exist, the text itself does not contain specific examples. Generally, these errors can occur at any stage of the minting process and are classified into a few main categories.
One major category is die errors. These happen when the die used to strike the coin is flawed. Perhaps the most famous example is the 1937-D "3-Legged" Buffalo nickel, which resulted from a mint employee over-polishing a damaged die, accidentally removing the bison's front leg. Other die errors include doubled dies, where design elements are visibly doubled, and repunched mint marks, common on older coins where the mint mark was hand-punched into the die.
Another category is striking errors. These mistakes occur during the physical striking of the coin. This can result in an off-center strike, where the design is not properly centered on the planchet, or a broadstrike, where the coin is struck without its retaining collar, causing it to be wider than normal. A strike-through error occurs when a foreign object, such as a piece of cloth or a wire bristle, comes between the die and the planchet during the strike, leaving an impression on the finished coin.
Finally, there are planchet errors, which involve the blank metal disc before it is struck. A clipped planchet error happens when the blank is punched from the metal strip in a way that it overlaps a previous punch, resulting in a coin with a curved piece missing. It is also possible for a nickel to be struck on the wrong planchet, such as one intended for a different denomination, which results in a coin with an incorrect size, weight, and metallic composition. A more modern and well-known example is the 2005-D "Speared Bison" Jefferson nickel, which features a prominent die gouge that looks like a spear running through the bison's back.
