Topic summary
Postage Stamp Error
Extracted from the Wikipedia article Errors, freaks, and oddities.
Errors
A postage stamp error is any of several types of failure in the stamp printing process that results in stamps not having the intended appearance. Errors include use of the wrong colors, wrong denominations, missing parts of the design, misplaced or inverted design elements, etc. The term "error" is typically reserved for obvious failures in the production process that (potentially) replicate over many stamps, while unique errors or poor quality are known as "freaks" or "oddities". Printing plate flaws, such as cracks, wear, or even constant flaws, and plate repairs, such as re-entries, are also not considered errors.