I doubt that it is a die scratch. Why? Because if would flow just across the fields of the coin if it were a die scratch. It flows over the devices. It may have been a light scratch that slightly split the plating and now it is raising when air reached the zinc underneath. If so, you should be able to see it when magnified with a higher power? Let us know. A shot of what it looks like when it flows over the date, 'R' on motto and the bottom edge of the bust would be helpful.