yup, Its a Pistol Stabilizing Device design by some shooters with a disability. So you can shoot is one handed better. Backed by the BATF. They are being sold separate for ~$135. I'd just put some foam in the brace and shoulder that thing...
Am I missing something or is this just a butt plate? Why would you need a stamp for a buttplate? Is it one of those bouncy bounce things that would shake the scope off its mounts?
That's one of those things I keep wondering if someone at the ATF will revisit and suddenly decide it is no longer legal to use for a pistol. Remember the original GSG5SD barrel shroud suddenly becoming an NFA item?