The case appears to be decorated in a manner similar to cloisonné, and then coated in niello. Unfortunately, the niello is not in the best of condition. I am not aware of any process for repairing the niello. The watch was used by someone who gave no thought whatsoever that anyone would ever contemplate trying to restore it. In fact, it looks to me as though someone set out to try to destroy it. The best hope for the dial would be to try to locate either another dial, or a donor watch. Given the condition of the dial and the case, I suspect the movement in the case likewise needs a lot of work. You don’t show a picture of the “works”, so it it tough to comment. With the right amount of money (read LOTS), and in the hands of the right shop (as in, try to find one), perhaps it could be restored. But it looks to me like a hopeless case. Too bad! If it was not so terribly deteriorated, it might have been possible to make a nice watch out of it. It would probably date from the early 20 th century.
