The BOCA basic mechanical code. (OCLC #2157951)
There are many reasons that materials might reside in a library’s special collections. They may be rare or fragile, but they may just be “a special collection” important to the library, like a reference collection which must stay in the library.
For example, our Design Library keeps building codes in its special collections. These are important to lawyers handling law suits involving buildings, as a building must only meet the code in effect when it was built, not necessarily the current one.