Those are called die flow lines. Keep in mind the grease that gets on the dies, is not used on the die, but on the machine. This leaks down onto the dies and get wiped off when seen. (Not often seen in the dies devices unless they look at the coins) So this pushing the the metal of the planchet forms the devices on the coin and the bust and reverse design. This pushing eventually forms these flow lines from this event over and over and over and over. Sometimes the a die clash happens and the dies are polished. That removes these flow lines for a time, bu eventually come back again. Each time the die is polished, the fields get thinner and the devices get shorter in height making them smaller in size. Then the fields die flow starts all over again forming from the same events over and over and over and over.