Error notes are examples of paper money that somehow managed to make it into circulation, despite the obvious printing mistakes displayed on their faces (fronts) and backs. It shouldn’t be too surprising that a certain number of error notes exist. After all, the U.S. Bureau of Engraving and Printing produces more than 10 billion notes a year, so a statistically tiny number of errors is hardly an indication of lax quality standards. But that very scarcity is precisely what makes error notes so interesting to collectors.
Errors are often organized by when the error occurred during its printing and handling. U.S. paper money produced during the 20th century is printed in three waves. The first printing creates the image on the back of the note, the second printing is for the face, and the third printing adds serial numbers and seals to the face. Other errors are due to the way the paper is handled (folding and cutting errors) during any of these printings. In all cases, the more dramatic and glaring the error, the more valuable it is to collectors.
The so-called “king” of paper-money errors is a note with mismatched denominations on its face and back, which means the mistake occurred during the second printing (sometimes a mismatch error is perpetuated through the third printing, too). A less-valuable but related error is a note whose face is inverted. Double printings at any stage are also sought, evidence that a sheet has gone through the press more than once. The result is usually a note whose face, back, or overprints appear blurry, since the images are not perfectly aligned.
Lack of ink, or too much, is a relatively common error. In general, the bigger the blank spot or smear, the more valuable the error. Offset printing errors refer to those goofs that result in some of the face appearing on the back of a note, or vice versa. Notes printed out of register are also fairly common. In these situations, the image intended for the back or face of a note might appear to be cut off at the top or bottom. In fact, the error is due to the printing of the note, not its cutting.
That said, sometimes an error in cutting is exactly the problem, although such notes are only considered valuable if you can see approximately 50 percent of bottom and top halves of the face or back, stacked on top of each other like a movie projector that’s gone haywire.
Finally, errors committed on the various types of large-size notes issued from 1861 to 1928 are even more rare than the ones that have been produced since. In general, that means that an error on a large note such as a Silver Certificate will be worth more than the same error on a modern Federal Reserve Note. Still, as always, there are exceptions to this rule. For example, the value of an error found on most National Bank Notes, which were issued from 1863 to 1935, generally has more to do with the inherent rarity of that particular National note rather than the type of error on it.