Now I'm intrigued, where did you find it? Does it have a tiny hole in the side?Have heard of a 17 ga shotgun but think it's quite rare. Again that's if it is what I think it is. Turtlefoot would know.
The stuff on the left may be part of fencing post attachments. Pot metal. I dig it and it sounds good. Took me a bit to figure out what it was because it had green paint or coating on it a couple times. Just a guess here!