Hi. I have opportunity to buy this Ajack 4x90 with 450£. I'm not very good with these scopes so if anyone can offer help identifying this I'd appreciate it. I've seen ajacks with focus ring and I'm wondering why this one doesn't have one. I've also seen that the turret locking screw is at the opposite side. Is there several models of ajack 4x90 or what is the case?