A graded stamp is a stamp that has a certificate giving its
grade, it can add to the stamps value
depending on the grade awarded by PSE.
A grade is an indication of how well the stamp is centered.
If the design of the stamp is well centered on the stamp
it will be awarded a higher grade. A stamps condition
and appearance contributes towards a higher grade as well.
Damaged stamps will recieve low grades.
If you have a stamp that is particularly
well centered, and is undamaged, that was issued before
1930 it is worth submitting to the PSE
for grading. If the stamp is used I would
make that before 1900.

A word about graded stamps and their value

When PSE started grading their stamps the
price of graded stamps sold at a substantial
premium over stamps with the same centering
but did not have the PSE certificate. I would
say it was crazy prices. Auction houses were
full of statements saying, "highest graded stamp"
or "only one other graded this high". These
statements sent the prices sky high and
encouraged others to see if their stamps would
grade as high.

With more stamps being graded by the hopeful
more stamps of a particular grade would come
on the market and what was once the highest
graded stamp became the fourth or fifth
highest graded stamp. A perusal of my
price tracking will find that the price of
graded stamps has plummeted. Their has
been a wholesale and dramatic reduction
across the board.

The PSE guide for prices for its graded
stamps is almost always higher than
the prices realized on this site.

The PSE's website can be found here.

An example of a certificate

EXAMPLES OF GRADES

GRADED 100

GRADED 98

GRADED 95J

GRADED 95

GRADED 90J

GRADED 90