050 Library of Congress Call Number

Field definition and scope:

Field 050 contains either a complete Library of Congress (LC) call number or an LC classification number assigned either by the Library of Congress or by other agencies using the Library of Congress Classification or LC Classification--Additions and Changes. The second indicator values distinguish between content actually assigned by the Library of Congress and content assigned by an organization other than LC.

The National level record requirement for this field is Optional.

Field 050 is repeatable.

Guidelines for applying content designators:

For indicator and subfield code definitions and examples, National-level (NLR) and Minimal-level (MLR) record requirements, and designator repeatability, see table below:

Position	Description	NLR	MLR	Repeatability
Field 050	Library of Congress Call Number	O	O	R
Indicator:
First	Existence in LC collection	M
#	No information provided	A
0	Item is in LC	A
1	Item is not in LC	A

Second	Source of call number	M
0	Assigned by LC	A
4	Assigned by agency other than LC	A

Subfield code:
$a	Classification number	M	O	R
$b	Item number	A	O	NR
$0	Authority record control number or standard number	O	O	R
$1	Real World Object URI			R
$3	Materials specified	O	O	NR
$6	Linkage	A	O	NR
$8	Field link and sequence number	O	O	R

Input conventions:

Content designator history:

First Indicator - Existence in LC collection

Value # - No information provided: Prior to the definition of code 4 in the second indicator position in 1982, the first indicator in the visual materials specifications was undefined. Visual materials records created prior to 1982 may contain a # (blank) meaning undefined in the first indicator position.

Second Indicator - Series call number (SE) [obsolete]: In the serials specifications, the use of the second indicator position to indicate the type of series was made obsolete in 1976. The values were: 0 (No series involved), 1 (Main series), 2 (Subseries), and 3 (Sub-subseries).

Second Indicator - Source of call number

Value # - No information provided [obsolete]: The second indicator was defined in 1982. Prior to that change, 050 was an agency-assigned field and contained only call numbers assigned by the Library of Congress. LC records created before the definition of this indicator may contain a # (blank) meaning undefined in this position.

Subfield $d - Supplementary class number (MU) [obsolete, 1981]

Subfield $0 - Authority record control number or standard number [new, 2017]

Subfield $1 - Real World Object URI [new, 2017]