Hi, I have a CP5, 5 shot CO2 that could either be an early one or a late one, I just don’t know? I have tried Walther and am waiting for a reply but wondered if anyone here knows of either a list or is there is a formula? I have found info on dating firearms through the proof marks but nothing for air weapons. The serial number is 01121. Any help or info on where to look or who to ask gratefully received.