The Scott Catalog, simply put, is the bible of philately. It first appeared in September of 1868, 28 years after the introduction of the British Penny Black. The Scott Catalog, even back then, purported to contain current values and information about every single stamp printed in the world at the time. The founder of the catalog, J. W. Scott, worked diligently to inscribe ornate descriptions of all American and international postage stamps.

Over time, the Scott Catalog grew from a 21-page pamphlet to a 5,000 page multi-volume set. Indeed, the Catalog has proven so central to the hobby of philately that early Scott Catalogs themselves are considered collectors items. Today, U.S. philatelists generally won't even consider evaluating stamps not listed in the Scott Catalog.

Of course, as J. W. Scott himself warned, no single publication can possibly codify and evaluate every stamp released. Micro-nations, local posts, and other mavericks publish stamps that never make the Scott listings. For instance, during the 1960s, a number of Gulf states, including the United Arab Emirates (UAE), published in-country stamps which never got included in the Scott Catalog.

All that said, unless you're cultivating an obscure international collection, you can employ the Scott Catalog to appraise the value of your stamps with great accuracy. The Catalog has copyrighted its enumeration system. Stamp collectors the world over know many stamps by their Scott College short hands. For instance, the CS(a) is the Scott number for the famous U.S. postal gaff, the Jenny Invert.