NSN (NATO Stock Number) structure

NATO Stock Number (NSN) Structure

At Leafield we will recognise Manufacturer's part numbers and industry standard part numbers but the main coding system recognised throughout our industry is the NATO Stock Number (NSN).  We thought it may be of some use if we provided you with a guide to the structure and meaning of the NSN.  The Item Identification Number (IIN) is what you would input into our stock search page to investigate whether we hold stock of any particular part number.  If you wish to know any more about what Leafield could do for you, please use the Contact link on the main menu.

A National Stock Number (NSN) is a 13-digit numeric code, identifying all the 'standardized material items of supply' as they have been recognizedby the United States Department of Defense. Pursuant to the NATO Standardization Agreements (STANAGs), the NSN has come to be used in all treaty countries, where it is also known as a NATO Stock Number. However, many countries that use the NSN progamme are not memembers of NATO i.e. Japan, Australia and New Zealand. A two-digit Material Management Aggregation Code (MMAC) suffix may also be appended, to denote asset end use but it is not considered part of the NSN. An items having an NSN is said to be "stock-listed".
(N.B. The mapping below is unofficial and used here for illustrative purposes only!) The format of an NSN might be described as follows:

abcd-ef-ghi-jklm

Each element, a through m, was originally intended to be a single decimal digit. As inventories grew in complexity, element g became alphanumeric, beginning with capital A for certain newly added items. By 2000, uppercase C was in use.
The initial subgroup, abcd, is the Federal Supply Class (FSC) or National Supply Classification (NSC). In theory, similar items would always have closely related numbers in this section of the NSN, no matter how the section is referred to. As the number of items has steadily increased and the system has become more complicated, it has not always been possible to keep similarity in numbers when the items are similar.
The ef pair is used to record which country was the first to codify the item—which one first recognized it as an important item of supply. This is generally the country of origin, meaning the country of final manufacture. The formal name of the field is CC for Country Code or NCB, because NCB also stands for National Codification Bureau. According to this system, for example, US is 00 and 01, Japan 30, Saudi Arabia 70, the UK is 99.
The nine digits, ef-ghi-jklm, comprise the NIIN (National Item Identification Number).
Originally, the ghi and jklm subgroups were envisioned to relate to one another in a way similar to the prefix and suffix of a local telephone number. However, by 1999, all attempts to preserve this relationship had generally been abandoned because it was too difficult.

The NSN is an expanded version of the older FSN (Federal Stock Number), which lacked the national-origin code labeled ef above, in the second subgroup. Items predating roughly 1975 in warehouses are frequently stenciled with FSNs. The FSN system originated in the US Department of War before or during the Second World War. As of 1998, the system was at least principally administered by the Defense Logistics Agency within the U.S. Department of Defense.