kashering old dishes

My wife inherited some ceramic oven to tableware from her late mother. It has not been used for at least 25 years. She does not know if it was Milchig or Fleishig. Can it be used in any way? Many thanks

I asked your question to Rav Ya'akov Ariel, Chief Rabbi of Ramat Gan, who answered that you can kasher them by carefully dipping 3 times in boiling water (while they are still boiling), but don't wash immediately in cold water (as is usually done), for that may break the dishes.