@Kelly Green I'm not sure. Can you try to move it (gently!) with a toothpick? If it doesn't move, it might be a "Dropped Element", but I'd need a better close-up. Chris
No it didn't move with a toothpick. Here is another picture a little closer. I'm sorry the quality is bad it is from my phone
My opinion is no. I think this is a 1958 (P) penny stamped into a cracked die or the planchet had this shape on it before it was struck. I think if mint mark strike would have disrupted the edge of the bust. In the case of your coin, it seems obvious the primary stamp of the bust cut straight through the anomaly on your coin....as the edge of the bust is clearly defined. Maybe the planchet was corrupt before it was struck?
No sir it is part of the coin. I'm sorry I wish I had a better picture I will attempt getting a better one tomorrow with a real camera.
It is definitely not a die break/crack. I also find it hard to believe it is anything post production. However, I have not a clue what happened to the die to cause that.