Librarians at MIT have been asked to review the monographs and serials which have remain to be reclassified from Dewey Decimal to Library of Congress. A significant portion of this reflects the history of atmospheric sciences, and many volumes contain observational data. What shall we consider as we make decisions about retention? How can we determine if the data, or publications in their entirety, are online? Could we create a workflow for the review of such material? How can we enhance our understandings of collections at other institutions, and possible digitization opportunities? This presentation will use examples to raise these questions and hopefully stimulate discussion.