This is a polisher.

It is from Egypt but the exact location is unknown. Stonemasons used a stone polisher to finish off the surfaces of carved stone, whether a building block or a stone vase. The polishing would smooth the surface and, on hard stone, give a shine to the object. This is a polisher. It is made from stone. It is between 3,300 and 3,600 years old, dating to the 18th Dynasty (1550-1295 BCE) in the New Kingdom.