If possible, catalogers should work toward submitting a proposal to establish a local term in the appropriate thesaurus. If the term is not eligible for inclusion in an established thesaurus, local terms may be used in 653 as outlined in the Metadata Standards Working Group's Local headings used at Harvard. Do not use 690; 653 is preferred, as it is a standard MARC field retained in the OCLC master record and indexed. Use of any local term must be approved by the Head of the Rare Book Section.
N.B. 69X fields are frequently found on legacy records for Houghton books and Widener transfers. When possible, these should be deleted and replaced with standard access points when the records are upgraded; but if they were added by a library other than Houghton or Widener, do not delete.