I have an early version, that I picked up as an unfinished belt buckle, that I completed enough to make it functional... mine ( unsure how the new ones operate ) has a pin that slides into one of the chambers, ( making the 5 shot gun into a 4 shot belt buckle ) it holds the gun pretty securely, though I guess I look at it as more of a toy, than as a back up, since mine reduces the capacity of the gun...
... but my "snake eyes" edition NAA mini looks pretty nice mounted on the buckle...