074 Subfield $z - Canceled/invalid GPO item number:

Subfield $z contains a GPO item number that has been canceled or incorrectly transcribed onto a bibliographic record. Subfield $z is repeated for multiple canceled or invalid GPO item numbers. Incorrect item numbers that GPO uses for distribution remain valid numbers in subfield $a .

Example:

074 ##$a1022-A$z1012-A