I referred this question to a friend who does competition BBQing. He refered it to a friend who is a cast iron enthusiast. Here is his reply.
Not sure of the manufacture of this fine pot, but it looks like something that was used in Camp Cooking. By camp cooking, was for the old lumber and mining camps up north, 1880 to right before WW 2. It made pouring the grease alot easier than the single handle skillet. I have two 15 inch skillets and they are a bit hard to manage (kicks my butt), but with two handles one can manage it. The two handle pot I traded to you, is an old restaurant style cooking pot and this looks to be a precursor to that model. Cast iron is cast, so being a homemade adaption eliminates that theory. However, it could have been braised welded on and will have the markings to indicate this.