Think the AO is irrelevant the older ones have thinner rets. Have looked through and owned dozens. The newer ones and factory refurbed ones had much thicker rets that bracketed on 5 mag like the older ones on 7. Factory set fixed parrallax ones at the end of me buying them all varied so much I gave up. You can age them by the writing style of the Burris logo on the scope. Can't remember which is which now.
Rick Ardern super low mounts ISP MK3 pellet launching platforms and Sightron 10 x 42mm telescopic sights.
Because it is not about how, but how many.