Apply the code "dcrmb" to records for microforms and digital reproductions of books if the descriptive portion of the record conforms to DCRM(B) (full, core, or minimal level).  If, however, DCRM(B) (full, core, or minimal level) is not used in all aspects (e.g., if the size of the book is not recorded in the physical description area), do not use the code "dcrmb."

See also:

Appendix A:  MARC 21 Descriptive Conventions Code