<s>"K" usually denotes steel frame in the Kahr line up. Don't know about "KP". </s>
D'oh. "KP" is how Kahr designates their original line of polymer-framed pistols. E.g. KP9093 is a polymer, 9mm, with matte stainless steel. I believe the rest of my post still stands more or less correct...
The CW line of pistols, IIRC, is their budget line, and either did away with or simplified a few things that the original line has.
I believe the lettering on the slide is simpler/different, the grasping grooves (or whatever you call them) at the rear of the slide are wider (and there are few of them), instead of polygonal rifling in the barrel there is...regular rifling (don't remember the specific type) -- stuff that made it simpler to make and thus less costly. I'd have to go to the website, but I believe that's what is different between the CW line and the others.
elb