ART II Scope questions

I have an ART II scope and I really don't know much about it. What I do know is that I can't get on paper at 100 yards - it shoots high with the elevation at the lowest setting. The optics are clear and the scope appears to function properly.

It also seems that the cartridge guide clip to mount the ART II is different from the "more recent" cartridge guide clip.

I just heard that they are built for different ranges and that that, at least in part, is due to the range ring you have (or the cam).

I'm interested in anything anybody can tell me. I've attached some pictures. If you need more, please let me know.

Thanks!