Even though a library tends to be about books and the written word, there are always things that help to enhance or supplement a collection but just aren't books themselves. These oddballs are lovingly referred to as "realia" and range from closely-linked-to-books items to ones that leave you scratching your head and trying to figure out the connection.
An exemplar of the "this fits nicely" object is a collection of printing plates for Stefansson's Adventures in Error. A more tenuously connected set of items is Daniel Webster's top hat and a pair of his silk stockings. Webster is an incredibly important Dartmouth figure and Rauner has a large number of Webster related items, though the hat and socks do push the connectivity limit. Finally, we have the New York fireman's helmet that belonged to Nelson A. Rockefeller, Dartmouth class of 1930.
Realia 81. Daniel Webster's top hat is Realia 37, the socks Realia 38, and Rockefeller's helmet is Realia 162.