The boy who found it is 5 years old. He discovered the treasure very much on purpose, as he was looking for artifacts. He spends all his available time searching for antiquities. To answer your question, so far he has not removed any of the surface rust, so no markings of any kind are known. What appears to be a flash hole is evident on the right hand of the breech end of the barrel is visible if one clicks on the photo. It looks like it came from the seldom seen flintlock half stocked shotgun.
Here are the flash hole, hooked breechplug and turtle front sight, I think.