Library of Congress >> MARC >> Authority >> 01X-09X >> 010

010 - Library of Congress Control Number (NR)

MARC 21 Authority - Full
October 2005

First Indicator
# - Undefined

Second Indicator
# - Undefined

Subfield Codes
$a - LC control number (NR)
$z - Canceled/invalid LC control number (R)
$8 - Field link and sequence number (R)


Unique number assigned to a record by the Library of Congress (LC) or a cooperative cataloging partner contributing authority records to the Name Authority Cooperative Program (NACO) database. The field is also assigned to records created by LC for the Library of Congress Subject Headings (LCSH).

LC control number is carried in field 010 subfield $a and field 001 (Control Number) in records distributed by LC's Cataloging Distribution Service.

An LC record may contain field 010 with a canceled or invalid control number of a previously-distributed record. A record may be canceled because it is a duplicate of the same heading represented by another record. The structure of the canceled/invalid control number is the same as that used by LC in field 001.




$a - LC control number
Valid LC control number (see explanation of structure of this number given below).
010 ##$an##84214414#
$z - Canceled/invalid LC control number
Canceled or invalid LC control number, including invalid NUCMC numbers.
010 ##$an##80022124#$zn##80014241#
$8 - Field link and sequence number
See description of this subfield in Appendix A: Control Subfields.


Agency Information - Field 010 is an agency-assigned field; it may be used only for an LC control number.
Punctuation - Field 010 does not end in a mark of punctuation.
Capitalization - Prefixes are always input as lowercase alphabetic characters.


LC control numbering system used with authority records has the same basic structure as that used in control numbers for Library of Congress bibliographic records (LCCN structure A). On January 1, 2001, a structural change will occur (LCCN structure B). The basic control number has been fixed in length at 12 characters and will remain that length. Under LCCN structure B the location of element parts is slightly altered to accommodate a four digit year. Under both structures, the prefix, year, and serial number are the basic elements required to make an LCCN unique.

LCCN Structure A (1978-2000)

Name of Element Number of characters Character position in field
Alphabetic prefix 3 00-02
Year 2 03-04
Serial number 6 05-10
Supplement number 1 11

LCCN Structure B (2001- )

Name of Element Number of characters Character position in field
Alphabetic prefix 2 00-01
Year 4 02-05
Serial number 6 06-11

Alphabetic prefix

Prefixes are carried in a MARC record as lowercase alphabetic characters and serve to differentiate between different series of LC control numbers. Prefixes are left justified and unused positions contain blanks. If no prefix is present, the prefix portion contains blanks.

010 ##$an##79051955#
[LCCN structure A; number on printed card: n79-51955]
010 ##$an#2001050268
[LCCN structure B; number in print form: n2001-50268]
MARC prefix: Explanation:
gf genre/form
n Name or subject authority record keyed by LC
nb Name or subject authority record originating in the British Library
nr Name or subject authority record originating in the Research Libraries Information Network (RLIN)
ns Sky River
no Name or subject authority record originating in the Online Computer Library Center (OCLC)
sh LCSH subject authority record keyed by LC
sj Juvenile subject authority heading keyed by LC and distributed in the LC Annotated Card Program
sp Subject authority proposal record in the LC catalog. (When it is approved, the record will be distributed with the prefix sh)


For control numbers assigned under LCCN structure A, the year portion consists of two digits representing the year the control number was assigned. In name authority records that were converted retrospectively by an agency under contract to LC, the digits 50 were used for the year for name authority records, and the digits 42 were used for series authority records. In subject authority records that were converted retrospectively from an LC internal format to MARC, the digits 85 were used instead of the actual year of creation. For control numbers assigned under the LCCN structure B beginning with the year 2001, the year portion consists of four digits.

Serial number

Serial number portion consists of one to six digits. Serial numbers of less than six digits are right justified and each unused position contains a zero. The hyphen separating the year and the serial number in LC printed products is not carried in the MARC record. For example, the serial number in control number 85-2 is carried as 85000002.

Supplement number (LCCN structure A only)

This character position was originally defined to carry a supplement number for dashed-on supplement entries in bibliographic records. No specific use of supplement numbers was ever implemented for authority records, thus, LC uses a blank (#) in this position.

001 n##80022124#
010 ##$an##80022124#$zn##80014241#

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