Error

A stamp error is a significant, unintended production mistake that makes a stamp clearly different from the version the postal authority meant to issue. Errors are among the most exciting finds in philately, and the most famous of them are among the most valuable stamps in the world.

Common Types of Error

• Inverts — part of the design printed upside down relative to the rest, such as an inverted centre or inverted overprint. See invert.
• Missing colour — one or more colours omitted from a multicolour stamp, leaving part of the design absent.
• Imperforate errors — stamps that should have been perforated but were issued without perforations between them. See imperforate.
• Colour errors — a stamp printed entirely in the wrong colour, for example because a plate was inked with the wrong ink or a cliché of one value was placed in the plate of another.
• Wrong watermark or paper — stamps printed on paper intended for a different issue.
• Double impressions — the design printed twice.
• Surcharge and overprint errors — double, missing, inverted or misspelt overprints.

Errors, Varieties and Freaks

Collectors often speak of EFOs — errors, freaks and oddities. The categories differ:

• Errors are major and usually consistent across a sheet or print run.
• Varieties are smaller but recognisable and often constant differences — plate flaws, re-entries, shades, retouches.
• Freaks are one-off accidents: a paper crease before printing, a sheet misperforated through the design, an ink smear.

Catalogues list major errors and many varieties; freaks are usually unlisted.

Famous Errors

• Inverted Jenny (USA, 1918) — the 24c airmail with the biplane upside down.
• Treskilling Yellow (Sweden, 1855) — a 3 skilling stamp printed in the yellow colour of the 8 skilling value; a single copy is known.
• British Guiana and other colonial inverts — inverted frames and centres on bicoloured issues.

Verifying an Error

Many “errors” offered for sale are fakes or manipulated stamps: colours can be removed chemically, perforations trimmed to fake imperforates, and overprints forged. Any valuable error should be accompanied by an expert certificate from a recognised authority.