Is the ball all brass or is just the insert? But in my not so expert opinion, the vast majority of cannonballs were made out of iron. So I think your ball is something else, but I don't know what it's supposed to be.
I had what I thought was a Civil War cannonball. Years later I found out it was only a ore crushing ball bearing. However it does make a great door stop.
Same thing happened to my friend, he called me all excited that he thought he found a cannon ball in the wall of a house. Sadly I sent him a picture of a shot put and that's what it was. What's with all these shot puts? Is everyone secretly trying out for the Olympics?
A member of our battery has quite a bit of land, and a couple of rentals. One of his renters came to him excited that she had found a civil war cannon ball by a creek on the property. He decided not to tell her that while it was a cannon ball, it was from one of the times we did live fires on his property.