What makes Gen 1 X6 "PPC" models different from regular X6 is the rear Aristocrat sight. In addition to being fully adjustable for windage and elevation, it also has 3 fixed
memory pre-sets for elevation.
This is helpful during competition when one encounters stages of a significance distance difference on the same day.
For example, they would set up one preset for 10-15y, the second for 20-15 y and the third one for 40-50y.......or some shooters also use these pre-sets for various types of ammo loads (bullet weight, powder type or amount - power factor etc.)
The Gen 2 PPC sight has 4 screws total. The Aristocrat sight is a bit more complex.