If it is determined by the TPG to be "natural" rather than artificial, there should be no conflicts to about MS-63, where eye appeal seems to play an increasing part of grading. When you read the PCGS grading book, they have paragraphs on the various types of "pretty" toning or "positive" toning as compared to obscuring or deep increasing blackish toning or "negative" toning. The extreme depth of toning will either not be graded due to inability to clearly see the surface of the coin, or will be labeled "environmental damage" If in doubt, use ANACs or ICG who will slab problem coins with explanation.
Jim




















