Abnormal reeding
This coin was struck from a collar die, which had either more than or less than the normal number of reeds. One of the most well-known examples is the 1921 Morgan dollar, which exhibits infrequent reeding.

Abrasion doubling
These coins were struck from dies that have been heavily abraded. The abrasion could have occurred inside the cavities of the design, including letters and digits. Such coins appear to have overlapping or doubled design elements. The abrasion could have occurred on the outside edges of the design, including letters and digits. The doubling is most commonly seen between the letters or digits and the rim. The best examples are the “poor man's double dies” of 1955. These coins are NOT the product of hub doubling and carry little, if any, premium. Abrasion doubling is a very common occurrence, especially on recent coinage. Thus it has little collector interest or value. Also see Die Deterioration Doubling.