This might help:

This show the position of the dies while creating your coin. When there is no planchet between the dies the die clash together. The two leave marks on each other when the fields of the dies clash together. The outlines of the devices can show in certain areas or all areas depending on how hard the dies clashed together. So you see outlines of the devices on the field areas on the opposite die. The dies are usually removed and cleaned/polished to remove these, but some coin may slip by before this happens or the dies don't get polished enough to remover all evidence of the clash.