National Codification Bureau

The National Codification Bureaus or NATO Codification Bureaux (NCB) are a NATO organization that oversees the management of the National Codification System (NCS).

Countries that participate in the National Codification System (NCS) follow common standards and techniques to assign National Stock Numbers (NSNs) to items of supply in their defense inventory. The National Codification Bureau (NCB) within each country centrally assigns their national NSNs. The assignment of an NSN denotes a distinctive item of supply; to eliminate confusion, the number will never be re-used.

National Stock Number
The National Stock Number (NSN) system was implemented on September 30, 1974. It was managed by the Defense Integrated Data System in 1975.

All NSNs are uniform in composition, length, and structure. Each is represented by a 13-digit number, which can be divided into two parts:

NATO Supply Classification Group
The first four digits are the NATO Supply Classification Group (NSCG) code. This relates the item to the NATO Supply Group (digits 1 & 2) and NATO Supply Class (digits 3 & 4) of similar items that it belongs to. Examples:
 * Group 10: Weapons
 * 1005: Weapons (from 1 mm through 30 mm).
 * 1010: Weapons (from 31 mm to 75 mm).
 * 1015: Weapons (from 76 mm to 125 mm).
 * 1040: Chemical Weapons and Equipment.
 * Group 11: Nuclear Ordnance
 * Group 12: Fire Control Equipment
 * Group 13: Ammunition and Explosives
 * 1305: Ammunition, weapons (1mm-30mm)
 * 1310: Ammunition, weapons (31-75mm)
 * 1315: Ammunition, weapons (76mm-125mm)
 * Group 30: Mechanical Power Transmission Equipment
 * Group 58: Communication, Detection, and Coherent Radiation Equipment
 * Group 65: Medical, Dental, and Veterinary Equipment and Supplies.
 * 6530: Hospital Furniture, Equipment, Utensils, and Supplies.

National Item Identification Number
The next 9 digits make up the National Item Identification Number / NATO Item Identification Number (NIIN).

The first two digits indicate the assigning country's NCB code - also informally called a "Country Code" or "Nation Code". Each country has its own two-digit NCB code, which were granted in the order the NCB system was adopted by that country. The United Kingdom (99), Australia (66) and New Zealand (98) are the exceptions; as a courtesy they were granted their status before the rest of NATO reviewed and accepted the NCB.

The United States uses "00" and "01" because they invented the system and were using it before the rest of NATO. NCB code "00" generally indicates an item in US inventory before 1974 (when the NSN was adopted by the US) and "01" indicates an item placed in US inventory after 1974. Canada's NCB "20" and "21" have a similar purpose. The numbers "02" through "10" are unassigned to reserve future catalog numbers for the United States' use.

The final seven digits are random. They indicate the code number for the unique item in that country's inventory. It will never be reused or changed. The NIIN has lately become alphanumeric (digits and uppercase letters) due to the vast array of items in the NSN, recently adopting the use of the uppercase letter C in place of "12" in 2000.

Federal Stock Number
The Federal Stock Number (FSN) was the codification system used by the US Government from 1957 to 1974. It was 11 digits long and was the same number as the NSN, minus the two-digit NCB code. The digits "00" were later added in the place of the NCB digits to virtually all FSN numbers to create compliant American NSN numbers.

The FSN was officially replaced by the National Stock Number beginning on September 30, 1974.