As this is a very technical area of stamp collecting, I have made use of the information obtained from two websites and I wish to thank both Wikipedia and MC Philatelics for their information in this regard.
The features assessed in determining the value of a stamp in relation to its condition are: Used or Unused, Gum and Centering and Margins. Other Faults cannot be categorised under these 3 headings. They are self-explanatory, but I have included some basic explanations.
Used or Unused
The basic difference between a Used or Unused stamp is the fact that the used stamp has been cancelled. The most common abbreviations used to describe these two basic conditions are:
O – Used
* – Unused
** – Unused never hinged
A key factor in the case of mint stamps, is the presence or absence of gum on the back of a postage stamp, or whether the gum has been disturbed. The following words will help us to understand the condition of the stamps in relation to the gum:
Mint never-hinged (MNH) is an unused stamp with its full original undisturbed gum with no damage done by a stamp hinge. For those who are new at this, a hinge is a small opaque piece of paper folded so that it can stick to a page, but also has a small gummed piece that sticks to the back of the stamp. MNH stamps sell at a premium if they are in this condition.
Lightly hinged (LH) is a mint stamp which was hinged but the gum was only slightly disturbed.
Heavily hinged (HH) is a mint stamp which was hinged and damaged in the process.
Hinge remaining (HR) is a mint stamp which has part of a stamp hinge on the back.
Original gum (OG) is a stamp with its original gum, but deteriorated by age.
No Gum (NG) refers to a stamp whose gum has been washed off.
Regummed (RG) Fresh gum has been applied to the back of the stamp.
Stanley Gibbons describes stamps with disturbed gum in the following way:
“large part o.g. Hinged mint stamp with the majority of the original gum
part o.g. Hinged mint stamp with less than 50% of the original gum.”
Further expressions used to describe gum condition are:
Disturbed gum (DG)
Gum skip – when the gum was applied it did not cover the whole of the back of the stamp
Centering and Margins
The following explain how well centred a stamp is and the width of the stamp’s margins:
Extra fine (EF) refers to a perfectly centred stamp with wide margins
Superb (S) is used for a perfect stamp
Very fine (VF) refers to a well centred stamp with ample margins.
Fine (F) refers to a stamp which is significantly offset, but still has 4 margins
Average (Avg.) is a stamp that has no margin on at least one side, and a portion of the design cut into by the perforations. These stamps are not usually collected or sold
Poor (P) Only really rare stamps (such as the British Guiana 1c magenta, a heavily cancelled stamp, soiled and cut to shape) are collected in poor condition.
SP – short perforation – when one or more of the perforation tips is not as long as it should be, but part of the tip is still present
PP – pulled perforation – when a perforation tip is completely missing.
SE – straight edge – when one or more edges of the stamp have no perforations.
RP – re-perforated. This is when perforations are added to one or more edges of the stamps.
Thin – a stamp with “a Thin” has an area on the back where the paper has been removed. This may be a tiny spot or even the entire stamp.
Gum bend – Gum crease – Gum wrinkle – when these stamps were made, the paper had a tendency to shrink but the gum did not shrink at the same rate, so the stamps would wrinkle. Generally these wrinkles do not lower the value of a stamp.
Face scrape – this is where a portion of the front of the stamp has been scraped away leaving a spot.
Inclusion – this is a piece of foreign material on the stamp which was pressed into the paper when it was manufactured. It is a brown or black spot on the front or the back of the paper.
I hope that this is of use and we welcome any comments below.