Cylinder seals are short pieces of semiprecious stones or, more rarely, metal, perforated along the axis so as to be suspended from a string and engraved with a decorative pattern or representational scene, and sometimes an inscription. When the seal was rolled over a flattened damp piece of clay, it left an imprint in high relief. The purpose of such seals was to indicate the authority of the person or institution who applied the seal impression, rather like a signature on a modern document.
The practice originated within the complex bureaucracies of the Middle and Late Uruk period (in the mid-fourth millennium B.C.). The pictorial scenes that refer to activities such as weaving, attending to domestic animals, hunting, and apparently ritual actions may indicate spheres of administrative competence within the Uruk economy. Thousands of imprints of such cylinder seals have been found on lumps of clay that were attached to door locks, jars, and other containers. From the end of the second millennium onward, cuneiformtablets could also be sealed. The iconography and artistic style of seal engraving naturally changed over time, which allows specialists to assess seals and sealings within a chronological and geographical framework.
Historical Dictionary of Mesopotamia. EdwART. 2012.