It should be laquer on the outside of the drums if the finish is original. I wouldn't use tung oil.......that is for unfinished wood, and since these have a finish already, that kind of nixes that idea. Here's what I'd do........and I've tried this myself with good success. If a drum has a laquer finish like an old Gretsch (or even the new ones come to think of it...) use automotive rubbing compound, with a soft cloth and by hand of course, never machine buff UNLESS YOU KNOW WHAT YOU ARE DOING in which case feel free...., and polish the drum by hand until the haze of the rubbing compound is gone. Then, use a good carnuba type PASTE car wax, not anything like Turtle Wax....it must be a CARNUBA wax, give the drum a coat of the wax, let it haze over then rub it off with a soft cloth. You'll be amazed at the shine you will get out of the old laquer finish! The rubbing compound will remove the crud and small scratched in the finish, and the wax will bring the luster back to the finish and protect it to some degree as well.....if its good enough for a 65 mustang, it should be good enough for a 65 Gretsch, right?