Lou,
You have a very interesting gun there. I think the Greg Martin auction description tells you about as much as anyone could say for certain. You are right about the case not matching the gun.

I’ve no details of the Morden Brothers but they would have been a retailer & general outfitter as you suggest – in the manner of Mantons.

Quite why the spirit of king Minguang was invoked is a mystery – does that engraving look as if it was done by the maker or added locally? A better photo of the proof marks & barrel markings would be good to see if possible as it seems as if there’s a lot of marks stamped on those barrels. It’s not easy to pick up all the marks in a photo – but getting the light at just the right angle helps a lot.

I feel that just who in the trade actually made the gun is of secondary interest compared to the interest from the information you already have which links the gun directly to a part of the world.

Regards
Russell