If it has an old lacquer finish, that could be difficult, if the lacquer has been exposed to plasticizers (cheap vinyl case, or wrapped in plastic for a period for some reason, e.g.) or simply degraded.
Naptha won't cut any cured finish that i know of, but is excellent on grease & oils.
Ethyl alcohol ("denatured" alcohol) is a little more aggressive to finish & less to grease and oils, but won't cut lacquer or any modern finishes. It will immediately damage an old french polish (shellac).
If the lacquer has started to soften, it will take a lot of slow cleaning to *maybe????* bring it back. Getting the gunk off (technical term) will remove some of the plasticizing effects, but won't cure it, pun intended, immediately. Maybe or maybe not long term.
Any solvent - try/test in small area and wait, first.
Good luck.
smt