`Birmingham made all the boxlock actions and most of the sidelocks too ` would be closer ! I think you have to remember that our interest takes us into a different world ie the past,and the trade did not operate in such a structured way as modern industry with its traceability .Work of individuals was perhaps identified by the way it was presented ,such as the way an action was filed to shape or parts of the mechanism were made etc.Those involved at the time would easily know who did what but perhaps had no interest in making it obvious at some point in the future .They were simply working to live and would produce product however the customer wanted it.
Bottom line is that there were few rules .HTh.