A number of doubles had second sets of barrels made for them as after market repairs. I've seen four or five different names used, such as Atlas, Noble... Countries of origin could be Italy, Belgium and perhaps Spain later or GB if you gun was worth it. Proof marks could narrow down when the barrels were added.
To me, putting a Simmons vent rib on any double gun is like putting false eye lashes on a pig, after you apply make up and lipstick. Does not make it better or even less ugly. Others have different taste or like gussied up pigs.
