Actually, the first known US made reproductions were some turned out in the 1920's and 30's by machinists who also worked in the auto industry. It is my understanding these didn't have serial numbers. This may be one of them that someone tried to make "authentic".
Also, I was told that there were some 1800's made repro's in Mexico, though the one I was shown didn't have a "Company" stamped on the side and the serial numbers were on the barrel and in front of the trigger guard.
There was a local gunsmith that made custom guns for people. When he died, there was a partially finished Patterson sold as part of his estate.