An auction catalog is a catalog that lists items to be sold at an auction. Auction catalogs for rare and expensive items, such as art, jewelry, postage stamps, and antique furniture, are of interest in and of themselves, for they will frequently include detailed descriptions of the items, their provenance, historical significance, photographs, and so forth. In some cases, auction catalogs are key documentation for rare objects that are in private collections, and make up an important part of the libraries of students and dealers of the rarities.
Each entry typically includes a "lot number" identifying each item uniquely, a detailed textual description, and either an estimated price, or a "reserve" price below which the item will not be sold. Photographs may appear with the entry, or grouped into a separate section of the catalog; for mass-produced items like postage stamps, the textual description may be considered sufficient.
As a combined information source and "sales brochure", an auction catalog must tread a fine line between accuracy and promotion. For instance, any damages or flaws must be described exactly, so that buyers cannot be claim to have been deceived, but at the same time the description will typically include words playing down the bad points (as in "brownish spot that does not detract from appearance" or "faint crease, as is common"). Similarly, special characteristics are also called out, such as "one of only four known examples of this type", or perhaps a photograph of an item of jewelry being worn by a famous person.
Auction catalogs may be sent gratis to favored customers, but the better catalogs will cost, sometimes as much or more than a regular book. These kinds of catalogs may in turn be sold by bookstores, or even appear as items in book auctions.
Some time after the auction is concluded, recipients of the auction catalogs will receive a "prices realized" document, a bare listing of the lot numbers and the prices for which each was sold.