The pix are so bad its hard to tell, but looks like dirt. Did you attempt any kind of cleaning? I'd say if you put it in mineral oil for a very long soak, you will in a few months come out with some nice detail. Hot peroxide bath then oil, same result, little faster. The hot peroxide won't hurt the coin, just the dirt. Sometimes the dirt enhances what little detail there is. Bottom line is you have what you have. NGC does shorts soaks in distilled water first, acetone next, then xylol. After that they reverse process if more cleaning needs to be done.
Great find, congrats!