Not nitro for sure, but probably a good hard urethane or polyurethane. I have an amber plus top and the finish is beautiful and hard. I don't think many, if any, Epiphones have nitro finishes stock. I like my plus top a lot. I put covered Seymour Duncan pickups in it: JB bridge and 59 neck. It sounds beautiful and plays really well. I'm not sure yet how it compares to my Gibson studio maple top faded, but it is no slouch.