I have had many older screw on casebacks that cannot be removed by even the best caseback tool without damaging the back. The original rubber seals turn to goop and glue the back in place. The solution - glue a 12" flat steel ruler on the back with original Gorilla glue using a soft clamp to hold it in place. Let it set up for 48 hours. Case needs to go in a vice - protected by a couple of old leather straps. Should turn right out. The ruler and Gorilla glue can be removed with "Goof Off". Soak the ruler and back in a shallow plastic cup for a couple of hours - it came right off. Goof Off is great stuff and well as Gorilla glue. Good luck, Craig
http://www.goofoffstainremover.com/what ... ue-residue
http://www.gorillatough.com/index.php?page=gorilla-glue