Update:
I got sidetracked in giving other details in my prior post (above), and forgot to mention something important about that ball.
Especially in the first photo, it appears to be covered with a thin layer of concrete/cement. That is worrisome, because I've seen other concrete-coated iron balls. They are the result of using iron balls to clean leftover concrete out of a concrete-delivery-truck's rotating tank.
Explanation: After the concrete-truck delivers its tankload to a jobsite, some wet concrete clings to the interior of the tank's walls ...and the concrete hardens when it is exposed to air in the empty tank. After a number of deliveries, it can build up pretty thickly inside the tank, significantly reducing the tank's capacity. How do you clean it out? Do you put a man inside with a sledgehammer and chisel? No. You simply put a bunch of iron balls in the empty tank, and flip on the rotation switch. The iron balls then tumble and crash around inside the tank, bashing the concrete off the interior walls.
My cannonball collection includes a big lump of concrete with iron balls in it. It was given to me by its finder after I told him what it (really) was. He thought it was from a civil war artillery projectile known as Canister. But actual Canister balls were contained in sawdust, not a concrete matrix. I've got a photo of it somewhere, which I'll post here if I can find it.
Mattmatt100381, does that ball have a thin coating of concrete, or is it just grey-colored dirt? (If it's just dirt, it will scrub off ...and concrete won't.)
