Any idea what the original surface finish is? Some similar pieces have rubbed oil like Danish or Tung oil. Others have a lacquer or shellac base. In an out-of-the-way place, see if alcohol affects the finish. If not, a tolulene or toluol rub down to get off wax and dirt, done outside, is probably a good place to start. The piece will get lighter since you will be taking off some of the dust and dirt. But then you will be able to see the grain better. As usual, take the safety precautions suggested by the manufacturer of the product that you are using.