Thanks for your reply, nchokie. We seem to have a few things in common; we’re both interested in historic artillery, and neither of us considers himself an expert on the subject.
I agree with Adrian that these gunades (with side trunnions) were almost exclusively manufactured for the private shipping industry. I also think Bob is right in saying that the raised crown was simply an advertising gimmick meant to attract buyers in that era. I’m also in accord with Bob in his thinking that the carronades (with an under barrel loop/lug) manufactured by the Carron Company for the military were regularly marked with identification. I don’t know if, or how gunades made by this company for armed merchantmen were marked. The reason I asked the question is because I thought you might have some information that would shed some light on this aspect of the subject.
There used to be an active member here (well informed about artillery) that owned an impressive collection of swivel guns, and one of them was in the form of an iron gunade. I remember that it had a similar type of raised crown on top of the barrel, but even though he researched it as thoroughly as he could, he was unsuccessful in his attempt to find out where it was made.