644 Subfield $5 - Institution/copy to which field applies:

Examples:

130  #0  $aArchives d'études orientales

644  ##  $af$5DLC$5DLC photo-offset reprint

130  #0  $aColección R

644  ##  $af$5DLC$5MH

See description of this control subfield in Appendix A:

Subfield code $5 - Institution to which field applies