None.. The only minor Mint Error is the Die Chip on the number 9. That is all. These are found on many 1957 Cents. I have about 6 of them. Here is an example from my collection -
I have the same 1953 D penny with the same marking in between the 5 & 3 but my 9 doesn't have the crud talked about above does this mean that this might be something more than what it was originally thought out to be????
The only way we can know is if you post pictures of your cent. Try starting your own separate thread.