Error Coins from the United States
Error coins! These coins prove that not all mistakes are â€śbad.â€ť Error coins range from mistrikes and offstrikes to broadstrikes and double dies. This is a very broad topic, but I will focus on double die coins. Double strikes occur when a planchet is struck twice, instead of once, and the two strikes donâ€™t align with each other.
One of the most famous US error coins is the 1955 double die penny, minted at the Philadelphia mint. Strong examples of this coin contain evidence of doubling in multiple points across the obverse, including the date and the motto, where the copper planchet was accidentally struck twice. Poor examples might have minor doubling, at a single point. My 1955 penny has doubling on the curve of the second 5 in the date, but doesnâ€™t have any noteworthy doubling otherwise. It obviously took a while to be recognized as a double die coin, because it is well worn and in average (or below) circulation.
Although not all error coins are high grades or obvious errors, those are the ones that command the high prices. Strong double die 1955s are valued at $2000+ in uncirculated grades, and still $1000+ in lower circulated grades. On the other hand, minor error examples, such as mine, are valued at about the value of normal 1955P pennies. This allows collectors to buy interesting and unusual errors, without paying high prices.
Error coins from the medieval period are far more common than those from the higher- tech modern times. Without the use of machines, they were struck with hammers, and multiple strikes might be used to get a good design imprint. Many medieval coins have doubling if you look closely, and arenâ€™t worth any extra. Those from the modern time period, where technology limits the number of errors, are much more valuable and rare.
Even with modern technology, double die wheat penny types are known from 1909, 1917, 1936, 1941, 1955 and 1958. This is in addition to other errors, such as broadstruck or mistriked coins, and errors in other denominations. Likely, it is as a consequence of producing billions of coins that some mint errors are able to slip past inspection.
When I got into error coins a few years ago, I acquired a broadstruck dime. It has a much more noticeable error than my penny, because it is much larger than normal. Because it was significantly more noticable, it was quickly removed from circulation and is a much higher grade (Unc) than my penny. Broadstrikes often occur because the collar, which limits how far the coin can spread, doesnâ€™t do its job.