A product code or product number is a reference code that some publishers use to label their publications and other products to aid identification. Product codes tend to be used by larger publishing companies with multiple product lines, and are particularly useful when there have been multiple books with the same title (e.g. for different editions), such as the many versions of the Monster Manual for Dungeons & Dragons.
Product codes are selected by the publisher according to that publisher's style. Product codes for role-playing game rulebooks and supplements will often be alphanumeric, starting with a prefix that refers to the publishing company or the game product. For example, the rulebook of Exalted first edition has a White Wolf Game Studio product number of WW8800, while Blades in the Dark has an Evil Hat Productions product number of EHP0030.
Other unique identifiersEdit
Published books will also have a unique International Standard Book Number (ISBN), which publishers purchase from an organisation called the International ISBN Agency. Whereas a publisher's product code may be applied to multiple products that are substantially the same (e.g. e-book, paperback and hardback versions of the same rulebook), a different ISBN must be issued for each. An ISBN is ten digits long if assigned before 2007, and thirteen digits long if assigned on or after 1 January 2007.