Error Notes: Oops the BEP Did it Again
The US government printed close to eight billion notes divided over six denominations last fiscal year according to the BEP.
Despite this large number, coming across an error note is still a rather rare occurrence. If you’re not actively searching for one, you could go your entire life without seeing an error note. This is mainly due to advancing technology at the BEP which finds and disposes of error notes before they leave for circulation. However it’s nearly impossible to find every error note and when they inevitably do get out they can make an otherwise ordinary note into something worth an exceptional amount. Here are a few examples of the various errors that can occur during the printing process.
The printing of a note occurs in three stages: printing the back, then the front then the overprint which contains the serial number and seals. During the printing process a sheet can slip or get jammed in the mechanical guides so the design gets shifted slightly, causing it to be misaligned with the other printing stages. These range from some minor ones to quite large ones.
Offset Printing Error
This type of error is basically a wet ink transfer. This occurs when the inked printing plate comes in contact with the impression cylinder. The impression cylinder presses the sheets into the printing plate. With the impression cylinder covered in ink, it now presses a mirror image of the design on the opposite side of a banknote. The offset printing can be partial or complete. When the front design is on the back of the note it’s called offset printing of front to back and vice versa.
Fold Over Error
A fold over error can occur when a sheet gets jammed during the printing process and folds. As it continues through the process, the note can be printed on again causing the print to be obstructed and displayed on another part of the note.
Obstructed Printing Error
This error can be very interesting (and valuable) depending on the circumstances. It occurs when something obstructs the printing process, for example some foreign object falling on a sheet before the printing plates press the design on the sheet. The result will depend on what stage the obstruction occurs, but normally there will be a blank spot on the note where the obstruction was. Very rarely you’ll encounter an obstruction error with the retained obstruction like this:
The most famous of these is the $20 Federal Reserve Note with a Del Monte banana sticker printed into it. This note sold for $25,300 at Heritage Auctions in 2006.
Double Denomination Error
One of the rarest errors that can occur, a double denomination error is often referred to as the “King of Errors.” This would occur when after a sheet has gone through the first printing stage and accidentally put through a different denomination for the second and third print, thus giving it two different designs. On national notes you can find a double denomination error combined with an inverted back error. This is due to different denominations being printed on the same sheet; the sheet would be place upside down on the second print thus making the back upside down and with a different denomination like this:
These are a few examples that can be found in US Error Note Encyclopedia by Stephen M. Sullivan along with several other examples. As errors can often be overlooked, it's never a bad idea to take a closer look.