This is a historic (index) list of United States Army weapons and materiel, by their Standard Nomenclature List (SNL) group and individual designations — an alpha-numeric nomenclature system used in the United States Army Ordnance Corps Supply Catalogues used from about 1930 to about 1958. The explains that the "Index of Standard Nomenclature Lists (...) covers – by groups, and subdivisions of groups – all classes of equipment and supplies, assigned to the Ordnance Department for procurement, storage, issue, and maintenance." The designations in this Wikipedia list represent so-called "major items". For each of the major items, there were separate, designated "Standard Nomenclature Lists" — extensive parts catalogs for supply and repair purposes.
In essence, the index was a list of lists. There could be numerous volumes, changes, and updates under each single item designation.
According to the Corps' Ordnance Publications for Supply Index of July 1943: Groups 'A' through 'N' covered "General Ordnance Supplies"; including group 'F' (Fire control, and sighting material), and group 'G' (Tank / Automotive materiel) Groups 'P' through 'T' covered "Ammunition" – for which there was an additional AIC code Group 'Z' was for "Captured Enemy Material", and Group 'OGS' indicated "Obsolete General Supplies". Group "Y", for 'Guided Missiles, guidance and control, launching, transporting, radio-controlled, and handling material, was added after July 1943
War Department Catalog
WD CAT. ORD 1 Introduction to Ordnance catalog
WD CAT. ORD 2 Index to Ordnance supply catalog
WD CAT. ORD 3 list of items for issue to troops, posts, camps, and stations. WD CAT. ORD 4 Allowances of expendable supplies WD CAT. ORD 5 Stock list of items WD CAT. ORD 5-1 Numerical index of manufactures part numbers, and drawing numbers WD CAT. ORD 6 Tools, and tool sets WD CAT. ORD 7 Organizational Maintenance Allowances. WD CAT. ORD 8 Field and Depot Maintenance Allowances. WD CAT. ORD 9 List of all service parts. WD CAT. ORD 10 tool load, and supply guide WD CAT. ORD 11 Ammunition WD CAT. ORD 12 Obsolete general supplies WD CAT. ORD 13 Parts common to two or more major items WD CAT. ORD 14-1 Interchangeability lists for tanks, and vehicles of related chassis. WD CAT. ORD 14-2 Interchangeability list Volume 1 Interchangeability list for ordnance, general purpose and combat vehicles (except full track vehicles) group 0-0800 Volume 2 Interchangeability list for ordnance, general purpose and combat vehicles (except full track vehicles) group 0900-2500 WD CAT. ORD 15-1 (Ordnance numbers) Cross reference list of ordnance part, and stock numbers (ten volumes) WD CAT. ORD 15-2 (stock numbers) (ten volumes) WD CAT. ORD 16 Captured Foreign Material