This amulet of polished hematite represents a headrest. Such amulets were common in Late Period burials, where their magic was intended to lift the head of the deceased at the moment of resurrection. The end of the base is broken off.
From Giza: G 7661 A, Room VII [Excav. date] April 27, 1929. Excavated by the Harvard University–Museum of Fine Arts Expedition; assigned to the MFA by the government of Egypt.
Harvard University—Boston Museum of Fine Arts Expedition