Two overdue books borrowed more than 50 years ago from a library in Portland, Oregon, have finally been returned, but the identity of whoever had them for all these years may never be known.The books "Basic Principles of Speech," and "Preface to Critical Reading," were placed in the Portland State University Library book drop earlier in October after they were checked out on Jan. 3, 1963, the library said in a statement earlier this week.The anonymous person who dropped off the tomes put a rubber band around them and a note saying they were borrowed for a high school speech class."It is now time for them (to) go back home. Outdated - yes - but I'll let you decide their fate now," the handwritten note read.Library officials said the books are so old, they are not sure what they will do with the long overdue items. The library does not charge fines for overdue books, but charges a fee for replacing lost books."If it were me, the guilt would have been relieved by returning them," Joan Petit, a librarian at Portland State University, said in a statement.The books were borrowed from the library of Portland State College, which became a university in 1969.