It is stated during the epilogue that Compulsion, film made about the Loeb & Leopold case, was released in 1958. The movie came out in 1959.
The two lead characters use a telephone with Touch Tone dialing-systems and other modern devices (TV remote controls, ballpoint pens, etc), even though the film is set in the early 1920's. The placement of such anachronistic objects was deliberate on the part of the filmmakers.