A friend just bought a Perazzi with a recoil device which acts like a G-Square in that the comb moves with the butt but it is NOT a G-Square. The butt pad is attached to the recoil device through a solid 3 to 4 inch high sliding piece rather than by a rod as with the G-Square. The posts to which the comb is mounted move with the pad but there is no slot which goes through the back of the buttstock. There is only an inch or so slot in the mounting plate of the posts which the posts recoil in.
I wish I had a picture but the gun is in for a release trigger.
What is it?