050 Subfield $b - Item number:

Subfield $b contains the item number portion of the series call number.  Organizations that use the Cutter-Sanborn Three-Figure Author Table may conform to Library of Congress item number practice by applying Subject Cataloging Manual:  Shelflisting conventions.  Subfield $b may also contain a copy (or set) number.

Example:

111  2#  $aInternational Kimberlite Conference$n(3rd :$d1982 :$cClermont-Ferrand, France).$tKimberlites

050  #0  $aQE462.K5$bI59