What Causes This Seperation - 09 Fy Cent - Plus Die Clash?

Since the fields are the highest part of the die they get the majority of the clashing. The die is polished in the fields to remove the clashing. This die was polished so much that the shallow parts of the devices ended up even with the field (the area around the hairline and nose). The clashing in the devises at the neck were not removed and can still be seen.

Steve: The outside edge of the die is the field. The devices are sunk into the die. But something missed is that the devices are not all the same depth. Some are more shallow than others so some devices in the mind range can be polished off. But sometimes the clash is very strong. The clash may affect into the mid depth area of the die. Leaving marks from the reverse die on the obverse shallow areas. Cleaning/polishing the die may remove some of the marks in the field, but sometime they clash marks are lower than the field and not removed.

Sometimes you may receive coins after a clash before the cleaning/polishing can take place. So there may be more than one example before they stop the machine.