Well, there is lots of information about this, and all other swamprat knives in the swamprat forum on this very site!
Sterile does mean that there is no logo or marking of any kind on the knife. I am not sure exactly why they dont mark their production models, cost, or perhaps its simply because it would be extraneous. The LM is the designator chosen to represent this particular iteration of the Howling rat. Look around some and you will find that it has changed over the years. Choil size, handle material, etc are different.