Every item in the vast military inventory, whether screws, aircraft, hoses or bathroom sinks, is classified with a National Stock Number, or NSN, and registered through a system of property books, which are established and maintained by each individual unit. Vehicles, for instance, carry an ID plate listing all pertinent information, including the NSN.
Identify the item you want to research and look up the national stock number, or NSN, or use the examples cited at Defense Data.com. An NSN is assigned by the Defense Logistics Agency to every item purchased or built, and is used to identify both the item and the end-user. There are currently millions of NSN's in use.
Study the structure of the NSN. It will appear as a group of 13 digits, configured as 0000-00-000-0000. For example, Olive Drab.com lists an M-998A1 HMMWV, or, in civilian speak, a military Hummer, with an NSN of 2320-01-371-9577.
Break down the 13-digit number. The first two digits alone represent the Federal Supply Group, or FSG. In this case, it is a vehicle. The first through fourth digits indicate the Federal Supply Class, or FSC, which in this example is a wheeled truck. The rest of the digits are the National Item Identification Number, or NIIN, which tells you what the exact item is. The first two of these digits represent the country of origin, or the NATO Country Code. The United States employs the digits 00 and 01. The last seven digits are the serial number of the item or piece of equipment you are identifying.
Check the data plate of the equipment. The example shown is for an old fashioned jeep, but it shows the configuration used today for every piece of equipment (and all components) used by, built and/or obtained by military contractors or other vendors. When filled out, the data plate for the above HMMWV can be precisely and immediately identified under any circumstances, whether in garrison or in a combat zone.