Curating the Code: The Secrets Behind Accession Numbers

When most people think of curatorial work, they imagine someone installing public, visitor-facing exhibits and displays. But curating can also happen behind the scenes, in storage spaces and database systems where much of the Museum’s collection is housed. Working in collections involves describing, categorizing, and caring for items in ways that help everyone understand their story, whether or not they ever appear on public view.

Spending time in the Collections Department reveals just how closely collections management and curating are intertwined. While collections management often focuses on organizing, storing, and tracking objects to keep them safe, curatorial thinking is essential behind the scenes as well. Decisions made during cataloging, like how to group objects, what to name them, or how to describe them, influence how these items will be understood and studied in the future.

Some accessioned collections are especially tricky to categorize. When a museum accessions a collection, it officially accepts the items into its permanent collection, assigns them a unique number, and creates a record to ensure they can be cared for and remembered. Museums often use number systems that have specific meanings to help track and organize these collections.

An accession number functions like a special code that helps a museum keep track of an object. For example, the number 2019.9.1.2 from the National Building Museum collection tells an entire story:

• 2019 indicates the object was added to the museum’s collections in the year 2019.
• 9 means it was part of the ninth group of items accepted that year.
• 1 shows it belongs to the first category or type of item in that group.
• 2 means it is the second object in that category.

The accession number helps museum staff know exactly when the object came to the museum, what group it is part of, and where it fits within the collection. Each element of the accession number acts like a clue, helping museum staff understand the object’s place in the collection. It functions like a library call number, but for museum objects. This system keeps collections organized so staff and researchers can find what they’re looking for.

It is typical for museums to use a three-part number system. In the example above, that number would be 2019.9.2. The four-part number, 2019.9.1.2, is an example of an accession number that the National Building Museum Collections Department uses when an accessioned collection is especially large or consists of a wider variety of items, making them more difficult to differentiate within the three-part number system.

Another numbering practice that museums might adopt is adding letters (a, b, c, etc.) to the end of numbers for items that belong together or are parts of a whole. This can apply to a few different scenarios, like a small box with multiple items or a single item with removable pieces. For example, if an item had multiple parts–like an award with a detachable name plate–cataloguers would add an “a” to the end of the main item’s number and a “b” to the end of the detachable part’s number. This version reads as 2019.9.1.31a and 2019.9.1.31b, helping staff members keep track of both items.

In addition to deciding how to categorize larger groups of items, such as using 2019.9.1 as the first portion of the number for 3D objects and 2019.9.2 for paper and archival pieces within the 2019.9 collection, it is important for cataloguers to use a smart system for ordering and grouping the items. For example, if there are twenty-three nearly identical granite rods within the collection, those should all be catalogued in a row. There shouldn’t be a miscellaneous belt buckle catalogued in the middle, breaking up the number flow. This level of organization makes it easier for collections staff to keep track of objects, refer to groups of objects in a numerical range, and logically rehouse or store items. It is also particularly important since collections staff often craft their own boxes and containers to store each item and group of items in a dedicated place.

Detective work and curatorial thinking are so important when determining what accession number to assign to each item in the museum’s collection. Even something as simple as writing a short object description could raise big questions. Choosing the right words to describe the object involves considering how people in the future will search for and understand it.

Working within the museum’s storage spaces offers a new perspective on how museums work. Every box and shelf holds something with a story, even if it is not on display. Making decisions about those objects–how to describe them, where to store them, and how to relate them to others–is its own form of storytelling. It demonstrates that being a curator doesn’t always mean being in the spotlight. Sometimes, it means making thoughtful choices behind the scenes.

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This post was written by Isabella Quartiere, Collections Intern during Summer 2025. To learn more about internship opportunities at the Museum, click here.