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A code designating the relationship of the reference number to the item of supply.

1Source of Control Reference. The number assigned by a design control manufacturer of an end item of equipment, including a Government activity, to a drawing that restricts procurement (1) to the specified item(s) described on the drawing and (2) to the stated source(s) of supply designated thereon. These restrictions are imposed on the cognizant design activity to ensure procurement of the only item(s) known as a result of test or evaluation to be satisfactory for the stated critical application. Includes only those drawings which meet the definition for Source Control Drawing in MIL-STD-100. (Applicable only to type 1, 1B, 2, 4 and 4B item identifications.)
2Definitive Government Specification or Standard Designator Reference. A part number, style number, or type designator included in or developed in accordance with a Government specification or standard which has the effect of fully identifying an item of supply. This code shall also be used for a Government specification or standard which, although not including part numbers, style numbers, or type designators, covers a single item of upply. These reference numbers may be coded with Reference Number Variation Code (RNVC) 1 in accordance with volume 2, paragraph 2.9.2.n.(4).
3Design Control Reference. The primary number used to identify an item of production or a range of items of production, by the manufacturer (individual, company, firm, corporation, or Government activity) which controls the design, characteristics, and production of the item by means of its engineering drawings, specifications and inspection requirements.
4Non-Definitive U.S. Government Specification or Standard Reference. Any Government specification or standard reference other than those indicated in code 2 as definitive references. This code shall be used for non-definitive Government specifications and standard references and non-definitive part numbers, type designators, and style numbers included therein which are coded with RNVC 1.
5Secondary Reference. Any additional number, other than a primary number (codes 1,2,3,4) informative reference (code 6) or vendor item drawing reference (code 7) assigned to an item of production or supply by a commercial or Government organization, which represents the same item of production or supply to which the National Stock Number (NSN) was assigned. The reference number may have had an RNCC of 1, 2, 3, 4 or 7 but has since been replaced in the item-of-supply concept of the NSN by another primary number.
6Informative Reference. North Atlantic Treaty Organization (NATO) Stock Numbers (CAGE Code 99995), Production Equipment Codes (CAGE 99998), and DoD Ammunition Codes (CAGE Code 99999) which may be related to NSNs. (Reference numbers for the CAGE Codes cited above shall be coded RNVC 9.)
7Vendor Item Drawing Reference (formerly Specification Control Reference). The number assigned by a design activity to a drawing that is not item-identifying, but which delineates existing commercial or vendor-developed items meeting all engineering and test requirements specified, without imposing additional test/engineering requirements not normally provided by the vendor(s). Includes only those drawings which meet the definition for Vendor Item Drawing in MIL-STD 100. Vendor Item Drawing References are administrative control numbers and shall not be used as part identification numbers.
8US/NATO-Reproduced Item Identification Number. A number representing a reproduction of an item of production by a NATO country (including the United States) for which authorization to use the NATO/National Stock Number has been granted by the originating country. The reproduced item represents the same item of production as the original item.
ADesign Category Packaging and Related Logistics Data Reference Number. The number of a document representing packaging and related logistics data requirements.
CAdvisory Reference. A number assigned to an item of production or supply not included in the item-of-supply concept to which the NSN has been assigned (e.g., an item that may have been used in the preproduction equipment design which has since been redesigned or replaced). Use of this RNCC is restricted to conditions where cross-reference is required to establish identification to an item of supply. Additionally, there is not direct relationship of the reference number to the NSN other than a Service/Agency individual decision. RNCC shall be used only in conjunction with RNVC 1.
DDrawing Number Reference. A number assigned by a design activity to a drawing or other technical documentation which identifies a drawing/document that is related to an item of supply or production but does not qualify for assignment of codes 1,3,5,7, or C. Code D reference numbers will not be used in item-of-supply determinations.
EReplaced Reference Number. A manufacturer's part number, government specification/standard or other design control reference number that is superseded, discontinued or replaced resulting from a cancel-use action on a NSN which was recorded with ISC 3 or E. This reference number is automatically moved and this code is automatically assigned, do not submit for cataloging purposes.