Here is an example of die breaks on one of my coins. Although it is not US, the concept remains the same. Note the left side of this coin, a litte thin line as a result of the crack in the die allowing metal to flow upward.
Thanks! It's my favorite of my cracks, and because it's a large brown coin, it's easier to see than the silver. I would have posted a picture of the other side but I couldn't find it on my laptop.