024 STANDARD RECORDING NUMBER (NR)
Indicators First Type of standard number or code 0 International Standard Recording Code 1 Universal Product Code 2 International Standard Music Number 3 International Article Number 4 Serial Item and Contribution Identifier 7 Source specified in subfield $2 8 Unspecified type of standard number or code Second Difference indicator # No information provided 0 No difference 1 Difference
Subfield Codes $a Standard recording code (NR) $c Terms of availability (NR) $d Additional codes following the standard code (NR) $z Cancelled/invalid standard code (R) $2 Source of number or code (NR)