This is a typical Early Dynastic cylinder seal, (grey speckled marble 2.6 cm) dated around 2500 B.C. It depicts a contest frieze. Crossing lions attack horned animals, flanked by trees. Prof. Lambert dates this seal to the Akkadian period, but according to Dr. Winkelmann (see links) it is clearly Early Dynastic.
Below the seal impression see a parallel, found at Kish.

Seal impressions

This cylinder seal (grey limestone 2.6 cm) depicts a contest scene. Among the fighting animals a man (Gilgamesh ?) is standing, holding up a dagger(?). In the other hand he carries a bow (?) This seal dates to the Early Dynastic III period (2600-2400 B.C.)Please see picture with parallels from Abu Salabikh and Mari ("Treasure of Ur").

One of the two main themes in Early Dynastic period are banquet scenes. This tiny seal (black serpentine 1.1 cm) depicts two figures drinking from a large vessel through drinking tubes, a scorpion and a snake (?) - a very archaic scene. Below see parallels from Fara and Tell Asmar.