Correct Coding of ISBN in MARC21 field 020 in RDA & AACR2 Cataloging with Examples

Several years ago the definition of $z of the 020 (International Standard Book Identifier) was expanded—it is now used for “structurally invalid” ISBNs (those that are too short, too long, wrong check digit, etc.) and also for “application invalid” ISBNs (ISBNs for a manifestation that would be described in a different bibliographic record). The LC-PCC Policy Statement for 2.15.1.7 provides the following instruction: Record ISBNs in $z (Canceled/invalid) of MARC field 020 if they clearly represent a different manifestation from the resource being cataloged and would require a separate record (e.g., an ISBN for the large print version, e-book, or teacher’s manual on the record for a regular trade publication). If separate records would not be made (e.g., most cases where ISBNs are given for both the hardback and paperback simultaneously), or in cases of doubt, record the ISBNs in $a (International Standard Book Number) of MARC field 020 Please remember to u...