A library at Britain’s University of Cambridge said a recent college reunion event ended with a surprise: the return of a library book that was 50 years overdue.

The Jerwood Library at Trinity Hall said the book, a 19th century atlas published by the Society for the Diffusion of Useful Knowledge, was dropped off at the library after a recent college reunion event.

The book was accompanied by a note explaining it had been borrowed by a Trinity Hall undergrad student in the early 1970s. The library said its records don’t go back far enough to determine the exact date that the book was checked out.

The library said the fine for the overdue book would have been more than $4,000 at the rate of about 27 cents per day, but the facility stopped charging late fees three years ago.

The library said in a statement that officials are “really grateful to the person who returned this book to us. It’s definitely a case of better late than never!”