I have had dishsoap and water destroy some decals on a Davis. I think I've tried Simple Green, can't remember for sure, but I think it was a little too strong also. Someone suggested, and I believe Miriam spoke highly of Turtle Wax Bug and Tar Remover. I was skeptical, but I've tried it and it really does WORK! Just don't rub too much or too hard, because the decals may be bonded better to the old shellac grunge than the are to the machine, and a few flakes may come off. Always test in an inconspicuous area 1st.