| ISC | Description |
| 0 | This item is under the specification control of the National Security Agency (NSA) and Defense Special Weapons Agency (DSWA) |
| 1 | This item is authorized for procurement as a result of a formal item-reduction study and accepted as a replacement for one or more items not authorized for procurement. In addition, in generic relationships, a code 1 item is related to a code 2 item |
| 2 | This item is authorized for procurement and has been included in an item-reduction study and which initially does not replace an item not authorized for procurement. In addition, in generic relationships, a code 2 item is related to a code 1 item |
| 3 | This item, as a result of a formal item-reduction study, is accepted as not authorized for procurement |
| 5 | This item is authorized for procurement and has not yet been subject to item standardization, or items under the specification control of National Security Agency (NSA) |
| 6 | This item is authorized for procurement and is in a specific Federal Supply Class (FSC) or item name grouping consisting primarily of items which are one-of-a-kind; therefore, little or no potential exists for elimination of items through formal item-reduction studies |
| 7 | NATO use only; This item is authorized for procurement and has been included in an item-reduction study but an intelligent decision could not be made due to lack of sufficient technical data |
| 8 | NATO use only; This item is no longer authorized for procurement and has been replaced by an item contained in a new or revised superseding specification or standard |
| B | This is a new item authorized for procurement, contained in a new or revised superseding specification or standard, that replaces prior items. This item will be assigned a Permanent System Control Number (PSCN) or, if a requirement exists, a National Stock Number (NSN) |
| C | This item is authorized for procurement and has been included in an item-reduction study but an intelligent decision could not be made due to lack of sufficient technical data |
| E | This item is no longer authorized for procurement and has been replaced by an item contained in a new or revised superseding specification or standard |