Cards for any given item were filed in multiple locations: under its title, author’s name, Library of Congress Subject Headings, and – where applicable – variant titles and names. The card catalog cases were removed and the remaining cards recycled in 2007.

Three varieties of card format found in the Olin union catalog: Handwritten cards in “library script,” used in the 19th and early 20th centuries; Manually typed cards; Printed cards generated from machines.

The Olin card catalog (as it appeared in the early 1960s) occupied half of Olin’s first floor public spaces.