I can’t wait to see an answer on this. When I was researching east Texas history for the Niamo Speck thing I’m working on it said there was a lot of civil war activity there and had pictures of what I think are “magazines” that are still there on the Caddo (?) river. This might be the real deal. If you don’t find anything out here you can also send the picture to the Fort Sill artillery museum, or I can do that for you.