In watching some Dead Weight last night I noticed that in the scene where Columbo has Holister open the crate for inspection.
Just as Columbo digs through the uniforms in the crate that were "neatly folded" there is a tight shot of Holister standing in front of a bookcase, just over his left shoulder on the top shelf there are two white books (among others) that if you freeze the frame you will notice are two of the Mrs. Melville books from Murder by the Book that Franklin gave to Columbo to read, might be old news to some but I got a kick out of it
Happy 4th to all the Columbo people out there

Yeah, they're just studio props. I've seen many used
on Columbo in other Universal productions, but I get the same charge out of identifying them.