Widener System

"Note that Widener uses two separate classification systems to shelve books: the Old Widener System and the Library of Congress System indicated by call numbers that begin with WID-LC. (...) In the Old Widener System, call numbers contain whole numbers and are separated by periods that do not confer a decimal value. (...) In Library of Congress WID-LC Classes, call numbers are separated by periods that do confer a decimal value."