It looks like an 80mm home-grown recoiless rifle, or something along those lines. For some reason, it makes me think of the old Karl-Gustav.
The rifle scope indicates that it is a creation of a talented ameture, and one with access to intersting materials, but anlmost any military would use a smaller, but just as efficient, set of optics.
Possible origins are Iran or Pakistan, they both have access to simple Chinese munitions that would work well on a rough & ready launcher tube like that.
This is all guesswork, for all I know, some Iowa farmer is looking for a new way to launch fireworks (altho the RPG in the foreground makes that unlikely).
Sorry, but the best I can say is that it is either (1) a Hollywood prop, or (2) the prototype of a very short-run local prodution.