The standardized part number used by the US Government for procurement.

NSN) The National Stock Number ( NSN) is a 13-digit number that the federal government assigns, for purposes of identification and inventory control, to every piece of supply, equipment, and material that it uses and buys. In a typical NSN, the first four numbers are the Federal Supply Code ( FSC), which places the item in a specific category. The second two numbers identify the item. The next two numbers identify the country that buys the item (00 or 01 is the code for the United States). The remaining numbers of NSN are referred to as the National Item Identification Number ( NIIN) and are used to index NSN

A number assigned by GSA to designate different types of goods and their attributes.