The Steyr Company, makers of Mannlicher-Schoenauer rifles, became one of the very early joint-stock companies and their rifle receivers show this transition. I don't have their centennary history just here right now to give me the date, but "AG" might be useful for approximately dating (or cross checking the assumed date), of certain guns made by makers like Inman Meffert who, for instance, began trade as early as 1839.
One contributor to another forum seemed to recall that Meffert, the makers of "Hubertus" marked firearms, were "acquired or merged with the Czech firearms manufacturer CZ in the early 1920's". Now, this may be a red herring, but I'm thinking that perhaps a trade mark showing two people holding hands could be that of a merged company, Meffert/CZ.
