Get your stamp collection appraised by going to the American Philatelic Society’s online Dealer Directory and searching for the dealer nearest to your location. All APS-approved dealers must abide by the APS Code of Ethics when appraising a stamp collection.
Appraisals can cost up to $100 an hour, as of 2015. Note that an official appraisal offers no guarantee that the stamps can sell on the open market for the amount the appraiser provides you. Because most stamps are common, an official appraisal focuses primarily on the most obviously valuable stamps and does not provide an inventory of each stamp. If you have inherited a collection, you may need an official appraisal for legal purposes.
Alternatively, consult a stamp catalog to determine the value of individual stamps in your collection. While stamp catalogs provide a fair estimate of stamp prices, they are only as guidelines as they cannot predict what the stamps would sell for on the open market. Like in any collectible market, stamp prices vary based on fashion, world events and trends. For example, the value of Princess Diana and Prince Charles wedding stamps soared after Princess Diana’s death, but they eventually evened out back to their normal value. The 50th anniversary of John Glenn’s space flight also caused a spike in the 1962 commemorative stamp.
For a more informal introduction to stamp prices, visit a local stamp show. The American Philatelic Society’s show calendar allows you to search by area and date for upcoming conventions.