The last picture shows that the whole section on the left side of the die crack for some reason is higher than the rest of the coin on the right side.
A retained interior die break is essentially a circular bi-level die crack that isolates an island of metal on the die face.
Very nice bi-level crack. I don’t have one of those, and I bet you’re glad you checked your change. For being 20 years old it looks in great shape.