This explanation is borrowed from @desertgem It is die deterioration damage. Even though the dies are tempered, after thousands of coin, the steel slowly deteriorates ( moving to the outer edges) and the letters appear elongate. Round tent stakes of air jumpers usually show such damage at the top of the stake. It doesn't a huge amount of force, just the force used to make a coin after maybe hundred of thousands of blows. Jim Hope this helps Reed and Sparkles
