M16A1 training aid?

[Anzac15]

Anyone out there have any idea what this may be? Belongs to a friend, I've never seen anything like it. Armorer's training aid?

[micmacman]

really weird , it gives you the sense it has a practical use but then you're looking at it trying to understand what , why the missing assist and sight parts , whats the metal under the barrel shank , whats the stainless extension,lol