685 History Note

Field definition and scope:

Field 685 contains information about the history of the use and meaning of a classification number. The history information contained in this field refers to the number in field 153 (Classification Number) of the classification record unless a 453 (Invalid Number Tracing) or 553 (Valid Number Tracing) field contains code a (History reference, field 685 used) in control subfield $w/3 (History reference).

If the tracing contains code a in subfield $w/3, the history reference refers to the number in that field. If there are two tracings in the record, both with code a in subfield $w/3, the number in subfield $a or $b identifies to which tracing the history note refers.

The information in this field is intended primarily for computer processing or to guide classifiers and is often not written in a form adequate for public user display.

Field 685 is repeatable.

Guidelines for applying content designators:

For indicator and subfield code definitions and examples, and designator repeatability, see table below:

Position	Description	Repeatability
Field 685	History Note	R
Indicator:
First	Result of change
0	Completely new number
1	Completely vacated number
2	Partially changed number
3	Reused after being vacated
4	Immediately reused
8	Other

Second	Type of history information
0	Relocation
1	Formerly
2	Discontinuation
3	Expansion
8	Other

Subfield code:
$a	New number - single number or beginning number of span	R
$b	Previous number - single number or beginning number of span	R
$c	Classification number - ending number of span	R
$d	Date of implementation at authoritative agency	NR
$e	Local implementation date	NR
$f	Title and publication date	NR
$i	Explanatory text	R
$t	Topic	R
$y	Table sequence number for internal subarrangement or add table	R
$z	Table identification	R
$2	Edition number	R
$5	Institution to which field applies	R
$6	Linkage	NR
$8	Field link and sequence number	NR

Scheme-specific conventions:

Dewey Decimal Classification

Content designator history:

Subfield $y - Table sequence number for internal subarrangement or add table [new, 2008]