Category:Stamp oddities and errors

**errors, freaks, and oddities**
	In philately, refers to all the kinds of things that can go wrong when producing postage stamps
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Listed or catalogued stamp oddities and errors.

In philately, errors, freaks, and oddities (EFO) 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 and includes both some of the most sought-after and expensive of all stamps and others that attract the attention of only a few specialists.

Stamps that have some major, consistent, unintentional deviation from the normal are considered errors.

The following is a list of the major types of errors.

Design error: The picture may be of the wrong subject, maps may show wrong borders, the inscription may be factually wrong, text may be misspelled, etc.
Value error or substituted subject: A die composed of multiple elements has the wrong elements mixed together, as for instance a low-value denomination being used on a design intended only for high values.
Omission error: Part of the stamp's design is missing.
- Missing color: Associated with printing processes which print the stamp in several different colors.
- Missing overprint: A stamp valid for postage only when overprinted but with a missing overprint.
Double impression: Stamp, or overprint, was printed twice, one impression offset from the other.
Invert error: Part of the stamp is printed upside-down.
- Inverted overprint: The overprint on the stamp is printed upside-down.
Color error: Stamp is printed in the wrong color(s).
Paper error: Stamp is printed on the wrong type of paper which, e.g., may have a different watermark or color than intended.
Perforation error: Perforations are missing on one or several sides or put in the wrong place (e.g. diagonally). As perforations may be removed by cutting them off, imperforate errors are collected in pairs.