The Content Designator History area of a topic provides a record of significant content designator changes.  The types of changes that are included are:

newly defined content designators that impact on coding consistency within a file

redefined codes and values

changes in codes and values for consistency across MARC specifications

changes in repeatability when it impacts on file consistency

restructuring

obsolete content designation

Obsolete vs. deleted content designators:

In the MARC formats, a distinction is made between obsolete and deleted content designators.

An obsolete content designator is one that may have been used in MARC records and that may continue to appear in records created prior to the date it was made obsolete.  Obsolete content designators are not used in new records.  An obsolete content designator is recorded in the Content Designator History area.  Content designation instructions are provided for retrospective conversion of records having data elements that would have been identified by the obsolete content designator.

A deleted content designator is not recorded in the history area and will no longer appear anywhere in the MARC documentation.  A content designator that had been reserved in MARC but has not been defined, or one that had been defined but is known with near certainty not to have been used, may be deleted from the format.  A deleted content designator is available for redefinition in a format.

See also:

Community Information Format:  Introduction