Atomic what?

I was flipping through this book, which I just brought home after coffee table duty in my office, and I ran across an ad for a child's atomic cannon. The ad claimed the toy was authentic, and sure enough, it looked exactly like this. That's 280mm - 11 inches of atomic love.

The Wikipedia article is here. Here is a video of a test of this thing (Wikipedia: "this was the first and only nuclear shell to be fired from a cannon"). They shoot it at 9:14, the projectile goes off at 9:31. And be sure to watch the ending credit, which is as good a summation shot as you could ask for (wallpaper candidate here).