Give only the dates for the materials on each of the multiple records and not for the entire collection.  Record the entire span of dates represented in the collection in a note on each of the records if this information is not already present in the title.

Record 1:

260 ## $c 1900-1910.

Record 2:

260 ## $c 1911-1921.

Both records:

500 ## $a Materials in this collection cover the span of 1900- 1921.

See also:

Appendix C7.  Cataloging divided into more than one record

Appendix C:  Collection-Level Cataloging