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The most important and easiest to understand element of grading is the relative centering of a stamp. PSAG measures the distance from the nearest edge of the perforation holes to the beginning of the design in 8 places (2 on each side of each corner) on a stamp. These measurements are then comparatively gauged against each other to develop the relative balance quotient. This numerical figure is then converted into a number ranging from 50 (severely off-center with one or more sides of perf holes cutting or touching the design), to a maximum 100 (perfectly balanced and equal margins on all four sides). In addition to the measured centering grade, the margin size affects the centering grade in two ways. Stamps with margins that are less than 75% of the average margin size for a given catalog number may carry up to a 10 point deduction. Conversely, stamps with margins 25% larger than normal carry an add-on adjective of  “J” for JUMBO. Prior to about 1970, the margin size on abnormally large stamps did not mean that much in terms of value. But Simmy Jacobs of Simmy’s Stamp Company began using the term JUMBO to describe these abnormally large margins and prices for these specimens skyrocketed. Ever since then, JUMBO has become part of the stamp collecting lexicon. Jumbo status can effectively double the price of a stamp vs. one with similar centering but normal sized margins. In summary, the centering and margin size generally determine the statistical maximum grade of a stamp. A faultless stamp would then have no deductions and be graded on aggregate centering alone with minor bonuses for exceptional color and impression. The following discussion will entail many parameters that can negatively affect the overall grade if they are found to be considered a fault of some magnitude. The level of affect has been determined by exhaustive analysis of 40 years of data regarding the value of faulty stamps. It is certainly a fact that some collectors view a short perf or a tiny pinpoint stain as minimal. On the other hand, many consider that quite detracting from the value. Our evaluation averages most of these effects to get an overall determination acceptable to the vast majority of collectors.


As mentioned above, color can affect the overall grade in both directions. A stamp with washed out or oxidized color (discoloration from the original shade by chemical reaction of the pigments), will certainly have the grade reduced. Normal acceptable color, shade and intensity should have no effect on the grade. Conversely, stamps with exceptional or unusually attractive color will have their grade raised.


Impression is the distinctiveness of detail in the engraved or printed lines of the stamp design. Stamps from worn plates show characteristically weak or fuzzy lines and are considered a ‘poor’ impression. Stamps exhibiting this poor quality are typically less valuable and a deduction in the grade is made.


In general, perforations on a stamp have an average length but are not exactly the same length all around. However, during the separation process, occasionally some perforation tips are not as long as the average. This may or may not be a problem depending on just how short they are. As a general rule, nibbed perfs’ (noticeably shorter perforation tips) or ‘short perfs’ (perf tips that have no length at all), have some significance to the grade. ‘Pulled Perfs’, where part of the stamp inside the stamp hole has been actually pulled out during separation, represents more than just a nibbed or short perf minor deduction. It may be responsible for reducing the overall grade below the 50 point level. Reperforating, the alteration of perforations on one or more sides, is considered a major fault and PSAG will not grade reperforated stamps.


One very small corner perforation crease on the tip of a corner perforation may or may not represent a significant deduction. However, anything more than that has a minor to moderate negative effect. Larger creases have an even more significant deduction. A large or heavy crease will like reduce the grade below the 50 threshold and not be graded.


A thin spec less than 1.0mm in size has a small point deduction. Thins that are larger than 1.0mm become problematic and have a significant impact on the grade of a stamp. Again, large thins will drop the grade below 50 in all circumstances.


A minor perforation tear has a significant affect and tears larger than 1.5mm will more often than not reduce the grade below the 50 threshold.


Over time, some stamps begin to exhibit tiny toned specs from a variety of atmospheric, chemical and bacterial sources. While these spots may be small, if visibly noticeable, they will have some very minor point deduction. Large toned spots or many small toned spots can have a much more negative affect.


Small stains are significant and large or heavy stains will result in a grade of 50 or not grade.


Natural wood pulp fibers (natural paper inclusions) from the paper manufacturing process are often imbedded in the paper of a stamp. If small and only seen on the back of the stamp, it usually has no effect. If easily seen on the front, this may result in a small deduction and may be mentioned in the opinion. Large 'carbon spot' inclusions are usually mentioned in the opinion and carry a significant grade deduction depending on the size and location. 


Perforation disc indentations (perf disc indents) are caused from the punched out paper from the perf hole (perf disc) during the perforation process being imbedded or denting the paper. After printing, sheets were stacked and pressed. Sometimes, the little perf discs were between the sheets and the pressure caused a dent in the paper of the stamps. Further, some of these discs on sheets with slightly tacky gum were adhered and imbedded into the stamp paper. This may or may not be a deduction depending on the severity, size and number of perf disc indents. During this stacking and pressing procedure of the completed sheets, a slight offset of ink from the sheet below may adhere to the gum, especially if the gum was slightly tacky from humidity or any other reason. This offset may result in a gum modification depending on how much offset occurs. A very slight amount is considered to have no effect. Stamps with more offset may result in a gum description of, 1. disturbed original gum or 2. part original gum.


In grading used stamps, the cancel may or may not affect the grade. Lighter cancels are preferred and heavy or obliterating cancels are not. Cancels may also penetrate the actual stamp paper or crease the paper from being struck too hard with the canceling device. In most cases this has a deleterious effect. The exception occurs when a stamp is canceled with a FANCY cancel. A clear strike of a fancy cancel will actually have a beneficial impact on the grade. Pen cancels, to most collectors and serious buyers, are not felt to have as much appeal as a standard handstamp or machine cancel. The exception, in rare instances, occurs when they are considered ‘fancy’ (ie- Weston ‘W’ pen cancel, etc.). Therefore, most pen cancels carry a deduction in the grade. However, if a “pen cancel” is listed in the Scott U.S. Specialized Catalog under “Cancels” in a stamps listing, no point deduction is made but pen cancel is noted in the ‘opinion’.


Many earlier issues of the United States stamps were printed with guidelines on the plate to aid in the alignment of printing or to guide the perforating machines after printing. On perforated issues, these guidelines show in part or in full on the perforation tips after separation. Stamps showing the guideline in full within the body of the stamp have the most significant reduction in grade. If restricted to just the perforation tips, the grade is reduced less. If the guideline just shows on a couple of perf tips or is barely detectable, only a slight or no deduction is taken. Attempts to scrape the guideline off the perf tips are considered an alteration and may be reason not to grade the stamp. An exception to this rule occurs when guidelines are present on the imperforate issues of 1851-56. On these issues, only a vertical guideline is present at the center of the two panes to act as a cutting guide when the sheets were separated into two panes before sale. These copies are highly sought after, either for their plating value (determining the position in the sheet, ie- Pos.43L2), or due to the fact that they are in the Sheet Margin and therefore the stamp has at least one huge margin.


The actual numerical grade of a stamp is not affected by the presence or absence of original gum. However, a modifier after the numerical grade will describe the state of the gum condition. These modifiers are as follows: ogNH – original gum, NEVER HINGED.

  • ogPH – original gum, previously hinged.

  • ogH – original gum, with hinge remnats(s).

  • pog – part original gum (not full original gum)

  • UnNG - unused with no gum on a stamp originally issued with original gum

  • dog – disturbed original gum (more than 50% of the area of the gum has been disturbed by hinge removal or other reasons.

Instances where the gum can affect the numerical grade or be mentioned in the opinion mostly emanate from the actual process of the gum drying after being laid down at the time of application. As the gum dries after this application, several things may occur, most of which are considered minor faults:

  • Gum Bends – light bends in the gum but no crease in the paper.

  • Gum Creases – bends in the gum that actually cause a crease or pucker in the paper in the affected area.

  • Offsets on the gum (described earlier)

  • Gum skips – specially in Flat Plate prints, may be present in one degree or another.

  • Tiny gum skips – if only a few tiny skips are present, generally there is no deduction.

  • Many tiny gum skips – At a certain point, many small gum skips begin to detract and will cause a small deduction in grade

  • Large gum skips – cause a deduction

  • Short gumming – a significant deduction is possible. (Short gumming occurs on stamps adjacent to the selvage around the sheet.)

The use of grading terms to describe the relative quality of a stamp has been going on since the very beginning of stamp collecting in the mid to late 1800’s. Beginning in 1987, a system was developed to finally begin standardizing the terminology and numerical grading of postage stamps. The system was built on the generally accepted definitions of terms and added the use of a numerical grading scale to further define the smaller gradations between the certain adjectival terms. Currently, the price differential between the lowest quality and the highest quality of a given stamp can be enormous. Further, seemingly small increments near the top of the grading scale can also account for very large differences. Complicating this entire exercise, collectors, dealers and auction firms can have varying assessments of quality of the same stamp since their personal preferences weigh differently on each of their pronouncements of a grade of quality. They just didn’t have a common reference point to speak the same language. Out of this need for a common reference, Third-Party Independent Grading was born. A standardized set of terms and numerical counterparts was devised to consistently describe all levels of quality from defective, all the way up to perfection. PSAG’s approach to grading is described below and is applicable to both mint and used stamps:

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