561 Subfield $3 - Materials specified:

Subfield $3 contains information that indicates the part of the described materials to which the field applies.

Example:

561 ##$3Family correspondence$aOriginally collected by Henry Fitzhugh, willed to his wife Sarah Jackson Fitzhugh and given by her to her grandson Jonathan Irving Jackson, who collected some further information about his grandmother and the papers of their relatives and Cellarsville neighbors, the Arnold Fitzhugh's, before donating the materials along with his own papers as mayor of Cellarsville to the Historical Society.