A National (or NATO) Item Identification Number (NIIN) is a 9-digit numeric code which uniquely identifies an item of supply in the NATO Codification System (NCS). The NIIN is often prefixed by the NATO Supply Class (NSC aka FSC) to form a National Stock Number (NSN), however the NIIN alone uniquely identifies the item, the FSC merely adds context by indicating the general classification of the item.