The earliest glyphic art emerged in the fertile plain of the Two Rivers around the beginning of the 5th millennium BC. Despite Mesopotamian civilisation having lifted the veil of the earliest phase of seals, complicated and yet well-arranged images and excellent engraving skills credit traditional Mesopotamian seals as the cradle for the Ancient Near Eastern glyphic arts.
Ninurtu was in his earliest worship a deity of agriculture, hunting, law and scribes. As his popularity grew, he became known as a formidable warrior, although still retained his agricultural attributes. He was closely associated with the Assyrian Empire but was worshiped as early as the middle of the 3rd Millennium BC by the Sumerians. He is sometimes shown riding a beast with the body of a lion and the tail of a scorpion. The figure he stands upon on this seal could thus be his famous mount or the lion-headed bird, Anzu.
For more about stamp seals, see our relevant blog post: Making their Mark