NIIN

The NIINClosedNational Item Identification Number - nine-digit number assigned to a part under the Federal Cataloging Program. It is the last nine digits of the National Stock Number. is a nine-digit number assigned to a part under the Federal Cataloging Program. It is the last nine digits of the NSNClosedNational Stock Number - a 13-digit number assigned to a part under the Federal Cataloging Program. The first four digits of the NSN are the Federal Supply Class (FSC) of the part. The last nine digits are the National Item Identification Number (NIIN) of the part..