I own about 10 featherweights and have cleaned, restored and sold more than that. What you are showing is the top shellac finish that was the protective coating placed over the decals, You will risk damaging the decals if you try to remove it. The best advice I can give you is if it will not come off with either plain water or light coat of machine oil leave it alone, you can wax over it and bring back some of the shine, but if you use any waxes with abraisives it will further degrade the finish. I use turtle wax. NEVER use anything with alcohol in it such as wipes as alcohol will dissolve shellac. Love your featherweight as she is and realize that these machines have a history of being loved and used, and worn finish just authenticates the age and the fact that some overzealous re-finisher hasn't been at work. If you will notice the worn areas are in the fabric path exactly where you would expect them to be.
