The recurring theme among the several American Can Company cans in my collection is innovation. The company had a long history and involved several large brands we know today (see the end of this post for more info.)
I've personally never opened a can like this, but it does seem like it would have been convenient.
You can read about the American Can Company at their wiki page. I also found this 1956 documentary called "Miracle of the Can" by the American Can Company. Pop a cold one, sit back and enjoy.