Is it a bolt action? If so, most likely, a K2.
Is it a pump action? Then a KP2 or KP3.
If it is a pump, then does it have a tube on the side that holds paintballs, or a feedneck? Does it take just 12 grams for an air source, or does it have a hose for connecting to an air tank, and maybe a bracket to hold that air tank?
See how complicated that can be without pictures? With pictures, we could probably tell you exactly what model it is and other info.