If it were mine, I'd wipe it down with damp cloths or paper towels. Not too wet, and dry it right away. If it cleans up OK, a coat or three of Galoot Mix will shine it back up. If it does not clean up well, match the color with Min Wax stain, let it dry for a few days and then a couple of coats of satin spar varnish. Poly urethane will look funny. The original finish is likely shellac. If it softens with isopropyl alcohol, it's shellac. You can still buy that at hardware stores, but I don't like it because it gets sticky in hot damp weather. Nice phone. Looks like it is in pretty good shape.