During the strike the center of the die makes contact first. When the metal starts flowing into the deep recesses of the die, it slow creates die wear on the die. The devices near the edge are the first ones affected. Then the central devices start showing die wear. (always towards the rim of the coin.) The date usually wears towards the right, LIBERTY to the left side of the devices. Motto towards the top of the devices towards the rim.

It is the direction over and over a few hundred thousands of time that creates this pattern of wear on the die.