The professor was having an estate sale, and was selling a large collection of vintage books, which were advertised in the classifieds of the August 11 issue of the Hill Valley Telegraph. The collection cost $200 OBO.
Whether Professor Beanes ever found a buyer for the book collection remains unrecorded.
Behind the scenes
- There are a couple of other classified ads above that of Professor Beanes in the closing frame of "Science Project", but these are unreadable due to being almost completely obscured by a flyer for Kruge's Pest Control.