001 - Control Number (NR)
MARC 21 Holdings - Concise
System control number assigned to a separate holdings record. For interchange purposes,
documentation of the structure of the control number and input conventions are provided
to exchange partners by the organization initiating the interchange.
An organization receiving a separate holdings record may move the control number of the
distributing system from field 001 to field 014 (Linkage Number) or to field 035 (System
Control Number), and place its own control number in field 001.