Cylinder seal and modern impression: demons and animals ca. 14th century BC Although engraved stones had been used as early as the seventh millennium B.C. to stamp impressions in clay, the invention in the fourth millennium B.C. of carved cylinders that could be rolled over clay allowed the development of more complex seal designs. These cylinder seals, first used in Mesopotamia, served as a mark of ownership or identification. Seals were either impressed on lumps of clay that were used to close jars, doors, and baskets, or they were rolled onto clay tablets that recorded information about commercial or legal transactions. The seals were often made of precious stones. Protective properties may have been ascribed to both the material itself and the carved designs. Seals are important to the study of ancient Near Eastern art because many examples survive from every period and can, therefore, help to define chronological phases. Often preserving imagery no longer extant in any other mediu