An update from Polaris Integrated Library Systems – $z in the 010 tag
Polaris ILS versions prior to version 3.5 do not allow an incoming authority record to overlay if the Library of Congress authority record is replaced by an older version of that authority record. When a newer record replaces an older record at the Library of Congress a “$z” with the old authority control number is added to the 010 of the new record. This tells the library that there was an old version of this record and it has been replaced with this new version. Prior to Polaris version 3.5, the Polaris system would not recognize the $z as the old record and the overlay would not take place.
According to Brad Rogers, Director of Implementation Services at Polaris, version 3.5 addresses this issue with a new dedupe rule added specifically for authority record importing. Version 3.5 is slated for release by Polaris in just a few weeks. The following Polaris importing setup screen reflects the change.