Question

an engraved piece ol clay used on seal

Answer 1

A seal is a device for making an impression in wax,clay,paper,or some other medium including an embossment on paper,and is also the impression thus made.
Its original purpose is to authenticate a document,a wrapper for one such as a modern envelope,or the cover of the container or package holding valuable or other objects.
In ancient mesopotamia carved or engraved cylinder seals in stone on other materials were used.These could be rolled along to create an impression on clay(which could be repeated indefinitely),and used as labels on consignment of trade goods,or for other purposes.