Philatelic expertisation is the process whereby an expert is asked to give an opinion whether a philatelic item is genuine and whether it has been repaired or altered in any way.

Forging and faking, regumming

Regummed stamp

In philately a regummed stamp is an unused stamp without gum, or without full gum, that has had new gum applied to the back to increase its value....

 and reperffing

Postage stamp separation

For postage stamps, separation is the means by which individual stamps are made easily detachable from each other.Methods of separation include:# perforation: cutting rows and columns of small holes...

 of stamps is common in the philatelic marketplace and increasingly buyers demand an expert certificate before buying a valuable item. Some items are so often faked or altered that they may be almost unsaleable without a certificate.

The process of expertisation

Experts may be individuals or committees but they will all follow a similar process to determine whether an item is genuine.

Stamps

Experts will attempt to determine whether a questioned stamp is a genuine example of a particular stamp issue; that is, whether it was printed at the same time from the same plate or stone as was that stamp issue. Among the factors they may consider are:

1. Is the stamp's design identical to those of genuine ones? Forged stamps almost invariably differ to a greater or lesser degree from genuine ones.
2. Is the size of the stamp correct?
3. Was the stamp printed using the same printing method, e.g., lithography
   Lithography
   Lithography is a method for printing using a stone or a metal plate with a completely smooth surface...
   
   , engraving
   Engraving
   Engraving is the practice of incising a design on to a hard, usually flat surface, by cutting grooves into it. The result may be a decorated object in itself, as when silver, gold, steel, or glass are engraved, or may provide an intaglio printing plate, of copper or another metal, for printing...
   
   , etc.?
4. Is the paper identical with the paper used for genuine stamps? Is the thickness, color, type of paper (laid or wove) correct?
5. Does the stamp contain the correct watermark
   Watermark
   A watermark is a recognizable image or pattern in paper that appears as various shades of lightness/darkness when viewed by transmitted light , caused by thickness or density variations in the paper...
   
    as do genuine ones?
6. Are the perforations
   Postage stamp separation
   For postage stamps, separation is the means by which individual stamps are made easily detachable from each other.Methods of separation include:# perforation: cutting rows and columns of small holes...
   
    correct, e.g., is the spacing of the perforations correct; are they of the same size, type and shape as those on the genuine stamp?
7. Is the color
   Postage stamp color
   The colors of postage stamps are at once obvious, and among the most difficult areas of philately. Different denominations of stamps have been printed in different colors since the very beginning; as with their successors, postal clerks could distinguish the Penny Black and Two pence blue more...
   
    of the stamp correct? Is it printed with the right inks? Some inks may react to ultraviolet light, for example.
8. Does the stamp have the correct tagging
   Phosphor banded stamp
   Phosphor bands were introduced on British stamps from 1959 as a replacement for the previous graphite lined stamps as an aid in the mechanical sorting of mail....
   
   ?
9. Does the stamp have the correct gum
   Postage stamp gum
   In philately, gum is the substance applied to the back of a stamp to enable it to adhere to a letter or other mailed item. The term is generic, and applies both to traditional types such as gum arabic and to synthetic modern formulations...
   
   ?
10. Even if the stamp was printed from the original plates or stone, is it a reprint
    Postage stamp reprint
    In philately a reprint is a new printing of a postage stamp from the original plates. A reprint is to be distinguished from a new print which is not printed from the original medium...
    
     made later, either officially or unofficially? There may be subtle differences in color, paper or design.

Experts also will ask whether the stamp been altered in any fashion:

1. Has the color of the stamp been changed? This sometimes can be done chemically.
2. Have perforations been added or removed to make it appear imperforate or coil?
3. Has the design been changed in any fashion? Sometimes, the denomination
   Denomination (postage stamp)
   :This article deals with the price of a postage stamp. For other meanings of the word 'denomination' see Denomination .In philately, the denomination is the "inscribed value of a stamp"...
   
    on a common stamp from a series has been changed to a rare denomination.
4. Has an overprint been added or removed?
5. Has a cancellation been added or removed? If the stamp is cancelled, is the cancellation genuine and of the proper period for the stamp?
6. Have other changes been made? The common 4 annas bicolor stamp of India
   Inverted Head 4 Annas
   The Inverted Head Four Annas of India is a postage stamp prized by collectors. The 1854 first issues of India included a Four Annas value in red and blue...
   
    has been altered by cutting out the image of Queen Victoria and remounting it upside down, or by chemically erasing the image and reprinting it upside down, to make the stamp appear to be the rare invert
   Invert error
   In philately, an invert error occurs when part of a postage stamp is printed upside-down. Inverts are perhaps the most spectacular of a postage stamp errors, not only because of the striking visual appearance, but because they are almost always quite rare, and highly valued by stamp...
   
   .

Experts will also attempt to determine whether genuine stamps have been repaired or cleaned:

1. Has a tear been mended?
2. Has a missing piece been restored?
3. Has a thin spot or hole in the paper been repaired?
4. Has the stamp been cleaned?
5. Has the stamp been regummed?
6. Have short or missing perforations been repaired?
7. Has a crease been repaired?

Covers

Among the factors experts may consider for a cover are:

1. The cover itself:
   1. Are there any repairs to the cover
      1. Sealed tears
      2. Stains removed by bleaching
      3. Cutting down one side of the envelope to remove a torn edge where the envelope was opened
      4. Erased pencil marks written by earlier stamp collectors
   2. Is the cover faked:
      1. Is the paper from the time period when the cover went through the mail?
2. The stamps on the cover:
   1. Are the stamps genuine or forged?
   2. Are the stamps correctly used? For example, using a stamp years after it is no longer valid for postage
   3. Have the stamps been repaired (cleaned, bleached, reperforated)?
   4. Have the stamps been removed from the cover and reglued to it? Usually done to identify rare varieties of the stamps
   5. Have stamps been removed from the cover?
   6. Have stamps been added to the cover which were not present when the cover passed through the mail? For example, adding a rarely used stamp to an existing cover to make an ordinary cover extremely valuable
   7. Have the stamps been removed and replaced with different stamps? For example, removing a stamp in excellent condition and replacing it with one having damage to the back, giving that the damaged backside of the stamp will not be visible.
3. The postal markings on the cover
   1. Are the postal markings genuine?
   2. Are the postal markings appropriate from the time period used?
   3. Have extra faked postal markings been added to the cover to make it more valuable?
   4. Is the ink genuine and from the time period used?

The tools of expertisation

Experts will often maintain their own library of fakes and forgeries, and they also have access to the records of past genuine items that they have seen. They will usually have a large library of philatelic literature

Philatelic literature

Philatelic literature is written material relating to philately, primarily information about postage stamps and postal history- Background to philatelic literature :...

 to refer to.

Scientific equipment is essential, including:

• Binocular and comparison microscopes
• Paper micrometers
• Ultraviolet and infrared energy sources
• Photometric colour determination equipment
• X-ray fluorescence and spectro-photometry equipment.

Common sense and above all, experience, are also vital.

Expert certificates and marks

Once an item has been examined, the expert(s) will issue a certificate giving their findings which will include identification, genuineness or otherwise and comments about any alterations or unusual features. The certificate will normally feature a photograph of the item and be signed. It may also be embossed or have other security features. In the past it was common for experts to sign or add their mark to the back of stamps, however, this is nowadays uncommon as it is by some regarded as an undesired alteration. In Germany (BPP) it is still common practise to sign many items, but generally not the most valuable.

There have been instances where expert certificates have themselves been faked and in the "Blüm Case", a forger produced false expertizing marks that were applied to German colony stamps

Postage stamps and postal history of the German colonies

This is a survey of postage stamps and postal history of the German colonies and part of the postage stamps and postal history of Germany, as well as those of the individual countries and territories concerned.- Overview :...

 and others.

Finding experts

In the United States, the Philatelic Foundation

Philatelic Foundation

The Philatelic Foundation is a philatelic organization granted a charter in 1945 by the University of the State of New York as a Nonprofit Educational Institution.-Location:...

, American Philatelic Society

American Philatelic Society

The American Philatelic Society is the largest nonprofit stamp collecting and organization of philately in the world, with almost 44,000 members from 110 countries...

 and numerous specialized stamp collecting organizations have committees who will perform expertisation for a fee. In Great Britain The Royal Philatelic Society London has a renowned expert committee which is also the oldest in the world, while German experts usually belong to the BPP. In addition, the International Association of Philatelic Experts (AIEP) is a worldwide organisation for independent stamp experts.

The results of expertisation may be challenged, and in some cases further research has shown the genuineness of an item considered a forgery, or vice versa.

External links

• Aspects of Philatelic Expertising - Part I by Simon Dunkerley
• Filatelia.fi list of philatelic experts (Includes more than 1700 experts, past and present, with their marks.)