Encyclopedia of Postage Stamp Errors and Counterfeiting
A comprehensive technical reference for amateurs and professionals — compliant with APS, BPA, RPSL, and Philatelic Foundation standards
In stamps printed in two separate processes (two-color or multi-layered), if the paper is inserted upside down in the second pass, the resulting internal design (center or frame) is inverted 180° relative to the other design.
Misalignment of two or more ink layers during printing results in a color appearing outside its designated boundaries. This ranges from a slight shift, only noticeable under a microscope, to a very large shift, visible to the naked eye.
- Major offset: The color appears completely out of character or covers part of the other design.
- Slight displacement: only adds value if it exceeds 2 mm and is noticeable.
- Always check that the displacement did not occur as a result of subsequent damage or moisture to the stamp.
The absence of a complete color on the stamp is due to the failure to feed a specific ink during the printing process. The color of the front, background, or value text may disappear entirely.
Passing a stamp sheet through the same printing press or one of its stages twice produces a duplicate design with slight or complete deviation. This differs from double minting in the world of currency in that it involves a single color or a complete layer of ink.
✅ True double printing
- Both prints are from the same ink.
- The shift is consistent in character.
- Clear under slanted light
❌ Double-sided printing forgery
- Subsequent manual printing
- The ink is chemically different
- UV rays reveal the difference
Overlaying is the printing of text, values, or designs over a completed original stamp. Its errors are among the most common and requested:
- Inverted Overprint: The text was printed upside down (180°)
- Double Overprint: The text was printed twice with a slight shift.
- Missing Overprint: The stamp was issued without the required overlay.
- Shifted Overprint: The text is not in its designated place.
- The missing overlay is the most frequently counterfeited — the overlay is chemically removed to produce “rare” stamps.”
The paper is folded before or during printing, then when unfolded it reveals: a white space (the part that was folded) and a repeated part printed from the back of the fold.
- Pre-Print Fold: The white space holds part of the inverted design.
- Post-print fold: No special collection value
- Distinguishing between the two types requires examination with a light microscope and sometimes ultraviolet light.
As the ink gradually runs out in the printing cylinder, the design imprint is left on the paper without visible ink — only raised or indented patterns that can be felt with a finger.
The stamps left the printing house without going through the perforation stage at all. This could be due to a machine malfunction or the stamps omitting this step in a particular batch.
- Imperforate Between: Perforation is absent only between two adjacent prints, while it is present on the outer edges.
- Imperforate Vertically: Perforation is absent vertically only (horizontally present).
- Imperforate Horizontally: Perforation is absent horizontally only (vertically present).
- “Scissor cut” copies look like Imperf but are worthless — check the straightness and smoothness of the edges.
Moving the paper during the perforation process produces holes in the wrong position — they may cut through the design or fall in the middle of the stamp.
Perforation gauge = the number of perforations per 2 cm. Compound perforation means a difference in gauge between the horizontal and vertical edges of the same pattern.
| perforation gauge | Description | Most common in |
|---|---|---|
| Perf 11 | Relatively rough perforation | Older American versions |
| Perf 14 | Smooth and close perforation | British and Commonwealth editions |
| Perf 13.5 | Common International Standard | Uno and many other Arab countries' versions |
Roulette is a notching technique that doesn't remove all the paper (no full perforations). It was used in Finnish and Dutch editions and in some early editions. This distinction is important for determining the correct value in catalogs.
A watermark is a design embedded in the paper itself during manufacturing. Its incorrect placement can produce very valuable variations.
- Inverted Watermark: The paper was fed into the machine upside down — one of the most valuable stamp variations.
- Sideways Watermark: The paper was inserted vertically instead of horizontally, or vice versa.
- Reversed Watermark: It was inserted from the back side of the paper.
- Absent (No Watermark): The stamp was printed on paper without a watermark — very rare
The same design may be printed on different types of paper at different times, and each type has a separate value in the catalog:
- OG (Original Gum): Genuine, undamaged gum — the highest value
- NH (Never Hinged): It never had a hangtag attached — highly sought after in modern stamps
- Regummed: The old glue was removed and new glue added — a forgery that drastically reduces the value.
- No Gum: Without glue at all — some older editions were printed this way
- Regummed is detected by UV and by comparing the gloss of the gum and its distribution pattern.
Since 1960, post offices have used phosphorescent lines or fluorescent coatings for automated sorting. Phosphorescent errors are among the most requested modern variations.
- Missing Phosphor: Error in applying phosphorescent lines
- Double phosphorus: Two lines instead of one, or a duplicate application
- Displaced phosphorus: The phosphorescent line is out of position.
Producing a completely counterfeit stamp (paper, ink, design, perforation). Famous historical counterfeiters:
A significant difference in the acquired value:
📮 Postal forgery
- It was designed for actual use on messages.
- Found used on real envelopes
- It has a high acquisition value, sometimes even higher than the original.
- Documented in major catalogs
🎭 Philatolic Forgery (forged to deceive collectors)
- It was made to be sold as a rare stamp.
- It has no educational value
- Destruction is required upon discovery
- Trading in it is a crime in most countries
- Regumming: Remove the used glue and add fresh glue to make the stamp look “unused” — the most common method.
- Added Perfs: Adding manual perforation to a cheap “Imperf” stamp to sell it as an expensive perforated stamp
- Cleaned: Chemically remove the cancellation seal to make the stamp appear unused.
- Reperfed: Re-perforating the stamp to improve perforation specifications
- Detection: UV for Regumming — Microscope for Added Perfs — UV and Chemistry for Cleaned
Printing a rare overlay on a cheap original stamp increases its value thousands of times. This exploits the fact that a truly rare overlay is on a genuine original stamp.
Exposing the stamp to chemicals (acids, bleaches, solvents) to change its color to resemble a rare and expensive color variation.
Ultraviolet (UV) lamp (254nm & 366nm)
An essential tool in every laboratory. 366nm detects phosphorus and added glue. 254nm detects chemical bleaching and paper types. Investment is mandatory. Cost: $30-$150.
Perforation Gauge
The perforation measurement is precisely determined. The British "Instanta" type is among the most accurate. It is essential for distinguishing perforation variations in the catalog. Cost: $10-$40.
Watermark Fluid / Oden
It temporarily makes the paper transparent to reveal the watermark without damaging the stamp. Oden or Donn fluid are safer. Cost: $10-$20.
Signoscope
Reveals watermarks with light without any liquid—best for protecting rare stamps. Won't damage glue or paper. Cost: $80–$200.
Double-sided optical microscope (Loupe 10× and 40×)
10x for general inspection and perforation. 40x for inspection of printing method (engraving, lithography, embossing), grid points, and fine details for counterfeiting. Cost: $30-$200.
Micrometer for measuring paper thickness
Paper varieties are sometimes distinguished by their thickness. A micrometer measures to an accuracy of 0.01 mm. This is useful for distinguishing between "thick paper" and "thin paper" in specific editions.
Basic reference catalogs
Stanley Gibbons (SG) for the Commonwealth. Scott for American and international stamps. Michel for German and European stamps. Yvert & Tellier for French stamps. Bale or Khalil for stamps of the Middle East and Arab countries.
📚 References and Academic Citations
This encyclopedia has been audited and compiled according to the technical standards of the following organizations:
- Stanley Gibbons Catalog – London.
- American Philatelic Society (APS) – Sorting Standards.
- Scott Catalogue – Error Coding.
- Royal Philatelic Society London (RPSL) Laboratories.
