It looks like a relatively well made pinfire, probably Belgian. I can't tell more without better pictures and/or description of the markings, etc.
One thing to look for is the Belgian proof mark with the letters E L G in an oval, probably on the back of the cylinder. If present, that would definitely confirm Belgium as the country of origin.
Value is not high. Those guns were common in Europe and are more a novelty than a collecting field in this country. They sell, on an average, for $100 or so in working condition. A nice one might run $200-300 but that would be about tops barring something really special, like a presentation piece.
Jim