Here is a coin pic I have pulled off Ebay. Granted the surfaces especially on the obverse right are porous and may be a cast copy I have used this picture as one that could fall with the Grey area. Look at the toning on the top left obverse. Colors do not really flow together . Also the colors look gobbed together. Now the reverse bottom right looks just as bad, but if you notice in the bottom left field the colors do not seem as predominant and if the toning on the reverse bottom left field were consistent rather than the painted look on the rest of the coin it may be passed off as authentic. Also naturally reflective & iridescent toning generally appears on surfaces that have not been over dipped or fooled with. Granted do not take that statement that any naturally toned coin has not been cleaned as there are many coins that have old cleaning which have toned, but the luster would be broken and any colors would not radiate as they would if the surface were original with a cartwheel affect. Lastly remember a lot of AT jobs are done to distract the eye from noticing cleaning, whizzing, porous surfaces especially on counterfeits. Chemical baths, low heat ovens fake bake colors, Bleach turns silver black, and leather will turn in a dark gray. Paper products with sulfur and humidity will naturally tone, but it can take years.
