Classification Numbers and Terms fields contain either one or more classification numbers from a schedule or table, as identified in 008/06 (Kind of record, code a for schedule or b for table), and associated caption(s), or a general explanatory index term, as identified in 008/06 (Kind of record, code c for index term only). A classification data record must contain one 1XX field, which is constructed according to the classification scheme that is identified in field 084 (Classification Scheme and Edition). Field 153 (Classification Number) is used if the record is an authority for a classification number or span and its associated caption and caption hierarchy. Field 154 (General Explanatory Index Term) is used if the index term cannot be accommodated in one of the 70X-75X Index Term Fields in a schedule or table record because it does not have an associated classification number.
Guidelines for applying content designators for field 153 are provided in the X53 Classification Numbers General Information section. Guidelines for applying content designators for field 154 are provided in that field.