Stamp grading: centering calculator

That is how PSE describes its system, and the other services work along similar lines. A graded stamp has been submitted to a recognized expertizing service, certified as genuine and given a number from 10 to 100. Faults bring points off. PSE also weighs eye appeal: color, impression, freshness and, on used stamps, the cancellation.

The Philatelic Foundation puts it bluntly in its grading booklet: centering is by far the most important factor for a sound stamp. That is why this tool starts there.

Centering alone never goes below Good (30) on PSE's 2009 grid. There, the in-between grades (60, 40, 20) and Fair and Poor come from faults. The Philatelic Foundation uses the same numbers with slightly different names: it calls 100 “Superb Gem”, 20 “Fair” and 10 “Poor”.

A 10x loupe and a fine millimeter scale work. So does a sharp, straight-on photo zoomed in on a screen: measure in pixels and use the relative mode. PSAG measures in eight places, two on each side of each corner, because a line of perforations is not always parallel to the design.

Normal margin size varies by issue. PSE gives US average margins ranging from 0.5 mm (Scott 330) to 1.5 mm (Scott 909), and some issues from the mid-1950s were laid out with unequal vertical and horizontal margins. Grading services also reduce the grade when margins are much smaller than normal for the stamp.

This calculator follows PSE's scale for perforated stamps. PSE treats the first US perforated issues of 1857 to 1861 differently: the space between stamps on the plate was sometimes narrower than a perforation hole, so the perfs can touch the design even on well-centered copies. Imperforate stamps are graded differently too, for example by comparing their margins with the space between stamps on the sheet. For those, treat the calculator as a rough guide.

PSE's guide says Fine needs at least 0.2 mm of white space on the narrowest side, Fine-Very Fine about 0.4 mm on stamps with rectangular framelines, and Very Good sits around 0.1 to −0.1 mm. From there up, it describes each grade by how the stamp looks: clearly off center, slightly off at first glance, a bit out of balance, boxed.

So the tool does the math where a published number exists and hands you PSE's own wording where it does not. If you see margin ratios quoted for stamp grades, they are not part of the PSE, PF or PSAG standards we checked.

PSE examines every stamp for creases, thins, color fading, toning spots and stains, tears, and reperforation or other alterations. On its grid, a Gem-centered stamp with a severe fault drops to 60. PSE does not grade damaged, altered, fake or counterfeit stamps at all, and PSAG will not grade reperforated ones.

Gum gets its own note after the number, such as OGnh (original gum, never hinged) or NG (no gum). It rarely changes the grade itself, but it changes the price.

PF, PSE and PSAG issue graded certificates. If you are not sure the stamp is worth the fee, start with our stamp appraisal guide or check a famous stamp's range in the stamp value checker. For the terms dealers use, read stamp grading explained.