Cogito. Singer cabinets were finished with shellac. To be sure take some denatured alcohol on a rag and apply to an area that will not be seen. If the finish melts with the alcohol it is shellac if not it is varnish or lacquer. You will find that the finish is shellac unless the cabinet has been refinished at sometime. Acetone will melt lacquer. If it is varnish lacquer or poly it will need to be strip.