6th Definitive Series - Errors, Flaws.Oddities & Constant Varietirs (EFO)

It refers to all the kinds of things that can go wrong when producing postage stamps. It encompasses everything from major design errors to stamps that are just poorly printed. Postal authorities generally take some care to ensure that mistakes do not get out of the printing plant.

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.

1. Missing color: Associated with printing processes which print the stamp in several different colors.

2. Perforation error: Oddities
a. Imperforate errors: Sometimes referred to as perforation error, this occurs when perforations are missing from one or several sides of a stamp.

b. Imperforate between: The external sides of a pair of stamps are perforated correctly, but perforations which should exist between the pair are missing.

c. Misperforation: Often known as a perforation shift, a misperf relates to any inappropriate puncturing of a stamp sheet. Caused because the sheet is not properly aligned with the perforating equipment, it can result in the perforation holes disfiguring the design of a stamp. (A stamp sheet may also be accidentally folded over before it's passed through the perforating machine. The folded part will become inappropriately punctured which can affect one or more of the stamps in a sheet and causes the design to be either partially printed or leave a blank space).

Freaks
A freak is a one-time mishap in the production process. Freaks include paper folds resulting in half-printed half-blank stamps, "crazy perfs" running diagonally across stamps, and insects embedded in stamps.