That's more of a curiosoty than a real gun.
It's actually a civil version of a gun developed for law enforcement, that was supposed to be something like a portable grenade launcher, fire tear gas grenades, loads of non-lethal-pellets, and such.
I don't know much about the police side of the matter, except that it was there (there is a livejournal post by an officer who handled one, with pics, I can try to dig up the link if someone's interested).
But the hunting version, as pictured, was in production only for a very short while in the early 1990's, and wasn't very popular.
Lots of people thought they wanted one, but the passion died as soon as they got one to handle.
Apart from being heavy and awkward, it's proofed for the equivalent of average 12 ga 3" loads, so owning one doesn't make much sense, does it?
There wasn't any loaded ammo offered, either, but one could reload the flare gun shells, which incidentally are exactly 4 bore.