For folks with old eyes:

It does look like some sort of surface residue is on this coin--could be clear nail polish, paint, or any of a thousand things. If you remove it, you may find differential surface toning between what has been covered and what has been exposed to the elements. This is a common enough
LWC that it probably isn't worth it to go through the whole bother unless you want to.
"If you climb a good tree, you get a push."
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz