the picture shows a classic fox. 98' fox's had a slight chaing in style with the 45 frame added. also classic foxes had a ball bearing valve which was upgraded to a poppet style valve by sending the marker into icd.
the fox is VERY simple in design. the body is 2 parts. the main body houses the spring and bolt and thats all the inerds. the rear part is the regulator
like everyone else said the cats are nearly the same. the alley cat though unlike the other cats could only put the tank vtl with the gun. others the front adapter would rotate to allow the tank to go along the barrel