It is probably a practice hand-grenade: iron casting with a hole in the bottom and the ability to put in a real fuse. You can buy then for about $30. We had one we played with when I was a kid.
“We had one we played with when I was a kid.” So did my siblings and I, but here’s the problem:
From the article:
“As it turns out, the grenade was still partially loaded and had the capability of doing harm.”