MARC classification records are distinguished from all other types of MARC records by the presence of code w (Classification data) in Leader/06 (Type of Record).  The MARC 21 Format for Classification Data further identifies three kinds of classification records in 008/06 (Kind of record):

   Schedule record - A classification data record in which field 153 (Classification Number) contains a classification number or span from the schedule itself, including a number which has been built from applying add instructions (008/06 code a).

   Table record - A classification data record in which field 153 contains a classification number or span from a table.  Table numbers generally cannot stand alone and are intended to be added to a base number to form a synthesized classification number (008/06 code b).

   Index term record - A record in which the 1XX field contains a general explanatory term in field 154 (General Explanatory Index Term) that represents a concept that is not related to one classification number or span (008/06 code c).

Related MARC fields or documents:

Leader/06  Type of record

008/06  Kind of record

153  Classification Number

154  General Explanatory Index Term

See also:

Classification Data Format:  Introduction