It's ball-shaped, and it's heavy, so is it a cannonball? That was the first thing that came to mind, but how can I be certain of what it is?

When reading about cannonballs, most of them retain their shape fairly well, even after fired from a cannon. So, what could this thing be?

Townsquare Photo by John Falcon

It was found in a field just off of Johnston Street back in the 1960s (a neighborhood has since been built on the field). Some kids were playing in the field (it had been plowed), and they came across this ball.

Townsquare Photo by John Falcon

It weighs approximately 12 lbs. The center of the ball is non-ferrous (isn't affected by a magnet), so I assume it's lead. There is an outer sleeve (or "skin") on the ball that is ferrous, so I assume the sleeve contains iron. You can see the sleeve being pointed out in this picture:

Townsquare Photo by John Falcon

Where can I take this thing to have it identified? I doubt if there is any value to a mostly lead ball, but I would like to know if I have a historic door stop (it's too heavy to be a practical paperweight!).

Here's a close-up of the "bottom" of the ball (I say "bottom" because it rests most solidly on that side):

Townsquare Photo by John Falcon

Is it a shot put used in track & field events, maybe?

Do you have any clue as to what this thing could be? Or as to where I should take it for identification? Any help is appreciated!