Just to be safe, use some diet coke on it. Q-tip and some light rubbing followed by some soaking and then scratching with a wooded toothpick. Maybe that will reveal some detail. If not, dry well and wet with some olive oil. Anything past that may take the writing/detail off. I have found out - the HARD way - that the writing on many old coins and tokens we find here is really crud or crust. It/they will come off when you clean it with a decent strength cleaner. So best to try a safe method first or when the crud comes off, so do the letters.
Daryl