It has a very small bore that appears to be for a toy gun. What makes me question that it is a toy is the fact that it has real heavy metal parts to it. I would not think that a toy would have parts like that it weighs about 2 to 3 pounds.
Old school toy guns were heavy as I remember. What makes me think this is a toy: the strike plate is square with a small hole in the middle, like the old cap gun caps. Holes in the barrel can be used for venting. Second barrel, if it appears that it was manufactured like the first barrel may be used for venting as well. OR...both barrels are simply decorative (non-functioning). That's a pretty cool find, non-the-less.