The AWC in the first post is a '98 production suppressor. That's my suppressor. It is registered in 9mm.
It is a barrel nut replacement mount, barrel stub slides into that "I" shaped piece, and the initial blast goes out those large holes. That "I" shaped part sits in the center tube, with the small holes in between the flanges on the "I" shaped piece. It screws in from the rear of the tube, butts up to an internal snap ring. There is a spacer ring, and all the cones slide in from the front, to the opposite side of forementioned snapring. Then the threaded plate that screws in and holds the baffle stack together.
Start an end cap into the center tube, slide the outer tube on, install other end cap, and tighten complete assembly together.