Originally Posted by DarkNinja
sniper 1 is similar to a sniper2 with a few differences. sniper 3 is a shorter body and has a banjo bolt setup for air. Sniper2=cocker, sniper3=minicocker where the asa is on the front block.
This page doesn't really deal directly with the question posed, but does give some more details regarding the distinction between the Sniper I and II: http://www.grendelsgear.com/cocker-dating.htm