What is used to identify items material that are not included in the federal catalog system in the Navy supply system?

The correct choice is identified as NICNs, which stands for National Item Control Numbers. NICNs are used within the Navy supply system to designate items that do not have a National Stock Number (NSN) and are therefore not cataloged within the federal catalog system. This system helps manage and identify these unique items, ensuring that they are properly accounted for and can be procured as needed for naval operations.

The other options represent different aspects of the supply and material identification system but do not serve the same purpose as NICNs. For example, NSN (National Stock Number) is assigned to items that are cataloged in the federal cataloging system, while ACRN (Advice Code Reference Number) pertains to supply advice within the Navy. CNF (Commodity Notice Facility) relates to notifications about certain item categories but does not specifically identify items outside the federal catalog system. Hence, NICNs are the appropriate identifiers for materials lacking an NSN in the Navy supply context.