Display constant for field 651:

-- [dash associated with the content of subfields $v, $x, $y, and $z]

The dash ( -- ) that precedes a subject subdivision in an extended subject heading is not carried in the MARC record. It may be system generated as a display constant associated with the content of subfields $v, $x, $y, and $z.

Content designated field:

651 #0$aWashington (D.C.)$xHistory$vPeriodicals.

Display example:

Washington (D.C.)--History--Periodicals.