Here are some examples of wording used for the 866 field in a serials Marc 21 Holdings record:
866 #0 $$8 1 $$a Shelved with newspapers in Periodicals
866 #0 $$8 1 $$a Library only retains latest "X" months
866 #0 $$8 3 $$a Latest 12 months in Periodicals
Detailed Holding Records instructions are on the Cataloging Guidelines > MARC Holdings Records page.
