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What’s in a Number?

Museum Accessioning 101

When looking at labels in your favorite museum, you might notice that the objects are referred to with specific sets of numbers. Sometimes a combination of numbers, letters, and years, these sequences can often seem like another language entirely that requires the skills of Nancy Drew to decode. It turns out, these sequences of numbers are actually museum accession numbers.

An acquisition (the purchase or donation of objects) by a museum does not automatically make the object(s) a part of the museum’s collection- they must be accessioned into the collection. And not every acquisition is accessioned! A museum collections management policy dictates what objects can be accessioned into the collections (another topic for another time!)

Museum accessioning is the process in which a museum officially adds an object to the collection. This involves all the documentation – from legal paperwork to establish ownership, to the internal documentation required to create a record for the new object(s). It’s during this process that the object accession number is created-  a unique identifier for the object. Like a call number helps you find your favorite library book, an accession number helps collections managers find objects in the museum collections.

We’ll take you through each step of the process, so next time you read a museum label and see these numbers, you will know what they mean and all the work that goes behind them!

Step 1: Assign the all-important number!


“Without a unique number that relates to specific files, an object is at risk of losing its context and information relating to its legal status.”- Museum Registration Methods.

When incoming objects arrive at the site, the first step we take is to assign the accession number. The accession number becomes the object’s unique identifier for a few different things. Primarily, the accession number helps staff easily identify an object. This is especially important when accessioning a set of similar objects, say multiple identical dinner plates. The accession number can also help differentiate between different types of collections if the institution has multiple collections. The unique accession number also becomes a means of tracking an object – tracking it in the database, its location,  and connecting the physical object to its documentation.

The most important thing for any institutional numbering system is consistency and standardization- it’s imperative to use the same system for all objects.

Most museums use a serial-style numbering process that looks something like this:

This method views each accession as a distinct group, starting with 1 and then going up from there, for as many accession groups as there are in a calendar year.  In the example above, the number sequence 2022.1, the .1 indicates that it is the first accession group of the year. If you had 50 accession groups in a year, the number would be 2022.50.

Your secondary number indicates the “groups” of objects that are in each accession group. For instance, in the example above, 2022.1.1, indicates there is only one object in the object group, while 2022.1.1-10, indicates that there are 10 objects in the object group.

Now let’s build on this. Let’s say the accession group includes 3 sets of different dinner plates. They were all donated together, which puts them all in the same accession group. However, each set should retain a connection to each other to establish their relationship.

Here this number sequence tells us that this accession group has 3 object groups, each with multiple objects. Something like a set of dinnerware, where there were 3 dessert plates, 4 salad plates, and 2 dinner plates, would have a sequence like this. The different types of plates should have their own numbers, but since they are all part of the same set, they retain the same base numbers.

When objects have multiple pieces that make up a whole or are multiple pieces that should remain in context together, additional letters or roman numerals can be added in. For example, a coffee pot with a removable lid would be numbered 2022.1.1ab, .1a for the lid, and .1b for the coffee pot base. This sequence tells us the two pieces go together and if for some reason they were ever separated, they could be reconnected.

When we accessioned this toiletry case that once belonged to Marion duPont Scott, the sequence of numbers got very layered!  To establish that all the pieces, although individual objects, belonged to the same set we used a combination of letters and roman numerals to indicate this!

At Montpelier, a system that includes alphabetical prefixes was introduced and so for consistency, we continue to use these prefixes. Some institutions may not use prefixes as they can sometimes be cumbersome if the prefix refers to a collection category, a geographical location, or a department. Our prefixes indicate different established collections – MF stands for Montpelier Foundation and indicates our permanent collection. (For example MF1999.39.1.) SMF indicates our study collection and then LMF stands for objects on loan. To learn more about the different types of collections, check out this project page!

Step 2: Documentation!

Once we’ve got the number assigned, we can now establish a paper accession file (yes we utilize old-school paper files). We record the numbers in the official record book and create a paper file. This is where we store all the appropriate paperwork and general information about the object that we want to make sure stays connected with the object. Research reports, notes from curators, and notes on the acquisition method all are a part of this documentation.

Step 3: Labels, Condition Reports, and Photography, Oh My!

Due to its importance, we certainly must make sure the accession number gets somehow physically attached to the object, but the method depends on the material.

  •  Ceramics, silver, glass, and other nonporous surfaces have the accession number printed on acid-free paper and then adhered to the object’s surface with an adhesive solution of B-72 suspended in acetone. This allows the adhesive to be removable. Essentially think of it as upscale clear nail polish.
  • Porous surfaces, like textiles or untreated wood, usually have the number applied with a paper tag with the number written in pencil, or with a cotton cloth label sewn on. Documents or books have their numbers written in pencil, or on acid-free paper tags that are inserted into the book.

After each object has its label, we condition report and photograph each object individually. The condition reporting process allows us to take a close look at the object, establishing a baseline for the object’s condition as well as recording any particularly descriptive physical characteristics. These can come in handy when trying to identify a particular object.

Step 4:  Database time

At Montpelier, one of our biggest Collections Management tools is our database! The database allows us to keep track of every object in the collection. We record its location history if it’s on display or in storage, any conservation or regular maintenance that we do to the object, and much more. Once we’ve completed the condition report and photographed the object, we create a catalog record for each individual object. This means if there are 30 plates, each plate gets its own record, that way if the plates get separated, each one can be tracked to its location.

Step 5: File, Storage, or Display

Once all the database catalog records have been added, and all relevant paperwork completed, the accession file gets filed away in our fire-proof cabinets. From there, the object(s) either go on display or we pack them for either temporary storage or long-term storage, depending on how soon they may or may not go on display.

Wrapping Things Up

As you might have noticed based on how long the section is, assigning the accession number is typically the most involved portion of the process. It may not be the longest portion – like say, condition reporting & photographing 60 + pieces of Chinese export porcelain  – but it certainly is the starting point for the process, and involves strategic thinking. For complicated objects or groupings, it feels like putting together a puzzle.

Now the next time you look at a museum label and notice a crazy-looking number, you know how much work is behind such a simple thing – and maybe you’ll take a crack at decoding it!