In order to properly identify old postage stamps, a stamp collection catalogue is necessary, according to 2 Click Stamps. There are two primary catalogues used by stamp collectors, the Scott Specialized Stamp Catalog and the Stanley Gibbons catalogue; these are used respectively in the United States and Great Britain.
There are several steps involved in correctly identifying and valuing both modern and antique stamps, according to 2 Click Stamps. First, a collector identifies the actual stamp, using a specialized stamp catalogue. After the stamp is identified, the level of centering is analyzed. Typically, the stamp is turned upside down and eyeballed for proper centering.
Determining the centering of the stamp allows the collector to assign a stamp grade; these range from extremely fine to below average. After grading, a condition is assigned, based on the original quality and preservation of the stamp.
The quality of the original stamp glue is also important in determining the current value. If the stamp is in extremely fine quality with mint condition glue, it maintains the highest value, according to 2 Click Stamps.
Other factors which impact the final value include perforation condition, degree of cancellation and the original rarity and current availability of the stamp.