(a) The following search descriptors will be required in all queries of the system for purposes of a background check:

(b) A unique numeric identifier may also be provided to search for additional records based on exact matches by the numeric identifier. Examples of unique numeric identifiers for purposes of this system are: Social Security number (to comply with Privacy Act requirements, a Social Security number will not be required by the NICS to perform any background check) and miscellaneous identifying numbers (e.g., military number or number assigned by Federal, state, or local authorities to an individual's record). Additional identifiers that may be requested by the system after an initial query include height, weight, eye and hair color, and place of birth. At the option of the querying agency, these additional identifiers may also be included in the initial query of the system.