Well, Oddball, you should be able to tell right away whether or not it is a DR or a DM. The difference is pretty big. Rosewood has a lot of wood grain throughout and Mahogany has smaller grain lines and is lighter. If it has the greek letter headstock, then it was made prior to 1978 and in Japan. There were no DM-7's as far as I know. DM-5 is highest, unless you talk about newer models like the D10 and others. Could be a DR-7 though. There is no real way to tell the number 1-7 though. You can only guess if the label is missing I think.