What is an Accession Number?
- Every institution that uses accession numbers will have its own specific type; there is no standard formatting across disciplines or institutions. Most accession number systems have blocks of letters and/or numbers separated by periods or hyphens. For example, the National Center for Biotechnology Information assigns molecules and proteins an accession number using a two-character prefix, an underscore and a numeric sequence from six to nine digits in length (AC_123456, for example).
- The object of an accession number is to convey as much information about a single item as possible using a predetermined code. Each section of the accession number has its own function. Sections may indicate one or more of the following: the object's location, the date it was acquired or produced, who is responsible for it, whether the item was donated or purchased, how the item was assembled and where a searcher might find more complete information about the object.
- Accession numbers make searching a vast collection easy. For example, the National Gallery of Art in Washington, D.C., assigns each work in its collection a three-part number indicating the year the museum acquired the work, a transaction identification number and an individual object number. Museum staff members can easily look up every piece acquired by the museum in a particular year or in a particular transaction. The museum also allows any Internet user to search the museum's collection by accession number.
- Marking precious objects with accession numbers can sometimes damage or even destroy the object. The International Council of Museums' subcommittee on musical instruments offers recommendations for affixing numbers to items that might be damaged, physically or aesthetically. These recommendations include writing the accession number in fade-resistant ink and covering it with acrylic resin, printing the number on fabric or paper and sewing it to the object, or engraving the number in a part of the object that's not visible to the public.
- When developing an accession system, institutions should be careful to create numeric codes that will always be unique, preventing duplication and the need for change or renumbering. New York's Metropolitan Museum of Art developed an initial accession system in which the first two digits indicated the year a piece was acquired ("72" meaning 1872, for example). But after the museum had been open for a century, the first two digits had to become four digits so pieces acquired in 1872 would have a different number than pieces acquired in 1972.