ES is English Shepherd. They are similar to a border collie. They are herding dogs and herd in an upright loose eyed manner. ES are very intelligent and have a good on off switch, but they are high energy. They are very loyal.
http://www.englishshepherd.org/

SIZE - Range:
height: 18 - 24", preference for 19 - 22";
weight: 35 - 65#, lean and fit condition
Comparison of Aussies, ES, and BC
http://www.nesr.info/whatbreed/