I have one that looks very similar that I picked up at a yard sale. It is marked Dixie Gun Works with their address and "Made in Belgium" on top of the barrel. It is about 16 gauge, and from what I was able to ascertain they were imported by Dixie about the time of the Bicentennial and marketed as "committee of safety" style muskets Somewhere around here I have a pretty old catalog from Dixie, one of the smaller ones, that has a picture and ad for it.
It appears that one has a brass barrel band and trigger guard, while the ones on mine are steel, and very simple affairs.