I created a reverse image of OP's coin, and then equalized the contrast. After applying a balance filter, I was able to see the following areas on the coin, which I circled in yellow, which may be what NGC is seeing, especially the one in the hair below the cotton bolls extending radially towards the northeast.
Just a guess. Here is my "flipped" picture.
This can be a useful way to see things that are hidden by toning, and also to see things that the camera does not see.

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"Most of the things worth doing in the world had been declared impossible before they were done." -- Louis D. Brandeis
Edited by paralyse
11/22/2015 9:57 pm