How Can I Tell If My Coin Has A Grease Fill Issue?

How can I tell if my coin has a Grease Fill issue?

When grease gets into the dies, it prevents devices from forming during the strike. This grease blockage can vary from affecting part of one device, partially fill one or more devices. Or can fill most of the coin. The ones with the 80% grease blockage are more interesting to collectors. It is easy to find single devices filled. But what do they look like and how can I be sure that it is what is affecting my coin?

A Struck Through Grease can affect any part of the die. Why? Because the dies devices are deep into the die. The fields at times can be affected with a blockage on the fields leaving the surface rough. So lets view some:

Here is an example of on device being affected on the reverse of a Wheat cent.

Note how this is a total fill block out that one device.

Many times we will find this on the date area:

Note how some devices are missing, while the one next to it is unaffected. That is form a localized Grease Fill on those devices.

Sometimes the dies are wiped down and the grease will fill, partly fill or reduce the height of a device in this manner:


Sometimes it will affect some areas and other times wider areas:

Other times it will block out most of both sides of the coin:


But how can you tell if this is a Grease Fill or something else? When a die gets partly block, the devices will be wider than normal and shorter in height.

Note on this coin that just certain areas of the die was partly filled. Other areas of the die is showing no fill.


How can this happen?

Perhaps the die was rubbed down with a cloth moving what grease that was on the die into certain areas of the die and leaving other areas unaffected. The area where the grease is, prevents the formation of the devices. But note on the examples above, the affected areas are wider than normal. Why? Because the devices are tapered. If they were not tapered, then the dies would not release the struck coins. So the devices are wider at the bottom and narrow at the tops of the devices. The grease filled areas prevent the device from being struck.
Here is a large percentage of a quarter that shows grease blockage.

How can I tell it is a Struck Through Grease error? Note the rim is present on the coin. If this were missing that rim, there may have been a different issue with this coin. But this shows the coin was struck through a blockage of grease on most of the die.
Other examples:








Grease on the fields of a coin:
On this coin you can see a disturbance on the strike on the fields:


Both sides were affected. The grease had some debris in the mix, thus the roughened surface.

Again what to look for on these is the widening of the devices, the shortened height of the devices. Hope this helps.
coophome= Struck Through Grease