I asked if they knew anything more about it, turns out to be Remington MCS.
Correct, that is a 10" Breacher in a Remington (made by Bladetech) SRD holster. The Kydex holster is designed to clamp the magazine tube/barrel between the fore grip and the frame. It is MOLLE compatable and can swith from right to left handed if you desire.Cool stuff indeed. 10" barrel and one of the sexiest pistol grips I've ever seen on a shotgun.