Thank you for submitting your item for appraisal. This appears to be a Thai stone rubbing or temple rubbing, possibly dating back to when one of your ancestors bought it, possibly as a travel souvenir in Thailand. Depicted is a scene from Thailand´s national epic, the so called The Ramakien or Rammakian รามเกียรติ์, "to the glory of Rama", which again is and adaption of the Hindu epic Ramayana. In most asian countries today it is illegal to do stone rubbings ( applying colour to the carving, putting a piece of paper on the carving and then rubbing the paper until most of the color is absorbed), which will eventually dry the supply. The estimate is based on similar offered or sold. "Asking prices" in the trade can be higher and vary.