signs Stock keeping unit (SKU) Track and trace National identification number National identification number is used by the governments of many countries as a means of tracking their citizens, permanent residents, and temporary residents for the purposes of work, taxation, government benefits, health care, and other governance-related functions. Chemistry CAS registry number IUPAC nomenclature Computing Cryptographic hashes Identity correlation MAC address Object identifier (OID) Organizationally unique identifier (OUI) Universally unique identifier (UUID) or globally unique identifier (GUID) World Wide Port Name Economics, tax and regulation Harmonized System Payment card number Unique Transaction Identifier (UTI) Universal Product Code Internet architecture and standards Best Current Practice (BCP) For Your Information (FYI) Internet Draft (I-D) Internet Experiment Note (IEN) Internet Standard (STD) Request for Comments (RFC) RARE Technical Reports (RTR) Legal Bates numbering European Case Law Identifier (ECLI) Gun serial number Legal Entity Identifier (LEI) Lex (URN) Mathematical publications Mathematical Reviews number Zentralblatt MATH identifier Research / Science Archival resource keys (ARK), with 8.2 billion ARKs issued. Digital object identifiers (DOI), with 200 million DOIs issued. Identifiers.org ORCID (Open Researcher and Contributor ID) Smithsonian trinomial Systematic name Transportation American rail transportation Reporting marks IMO number to identify sea-going ships International Air Transport Association airport codes IMO container codes according to ISO 6346 for shipping containers License plate number Maritime Mobile Service Identity (MMSI) UIC wagon numbers See also Numbering scheme References Names Unique identifiers