The first step in determining a stamp's value is to find it's centering, the balance of the stamp design within its margins. Currently there is no established system for grading or measuring centering, so “eyeballing” has become the standard. As a result, one collector’s definition may vary from another’s. If you are unsure of your stamp's centering, it is best to consult a professional philatelist.
Centering ranges from poor to jumbo as follows:
Poor—the stamp design is so far off center that a significant portion of the design is lost. On a poorly centered perforated stamp, the perforations may actually cut far into the design.
Poor stamps are usually not collected, because of their lack of value.
Average—a stamp whose design is cut slightly by the lack of space on one or two sides. On a perforated stamp, the punched holes may penetrate the stamp, but some outside margin will show on the perforation teeth.
Fine—a stamp with perforations clear of it's design, whose margins are unbalanced. A stamp may have its top and bottom margins perfectly balanced and it's left and right margins unbalanced.
Fine to very fine—a condition often used by collector's to identify stamps whose design position and margin balance fall somewhere between fine and very fine centering. Often written as FVF.
Very fine—a stamp's opposite margins may appear to be somewhat unbalanced, but the stamp design is closer to perfectly centered, than fine centered.
Superb—a stamp design that is perfectly centered. Superb stamps are scarce and, therefore, more valuable.
Jumbo—relative to the average issue, margins are largely over-sized. Jumbo stamps command high premiums.