This is more of a general question, I don't have any particular coin in mind, but I'm thinking along the lines of spots on the attached pictures (I don't own the coins pictured). I have noticed while looking at old copper coins (I've been looking at a lot of early 19th century ones recently) that some have blackish spots of varying sizes on them. One or two had larger black streaks and some had collections of scattered spots. How bad are such spots, even on certified and slabbed coins? Are they worth avoiding altogether? Or are they just considered not as aesthetically pleasing as spotless coins? An article I found online (the link ran away from me, unfortunately) said that black spots on copper coins greatly impact their grades and desirability, which made me think I should avoid them. Yet I've seen spots such as the ones pictured on coins graded AU and above. So I'm curious what others here think.
It should be mentioned that you may be surprised how many seemingly non-spotted copper pieces have been "enhanced" in very innovative ways, and is a "colorful" hobby for many coin doctors. In a TPG holder or not. As a practical matter, it is nice to find a piece that is not encumbered, but as a hobbyist, it does not bother me that much. If your pursuit is monetary gain, then don't purchase, because perception is 9/10 of the sale. Just a word of caution, if the piece is a pretty blush red/pink shade on the entire spectrum, chances are you should run. Fast. Other than that, I got nothin.
As a general rule, those spots will detract from the price and may detract from the grade given by a TPG. Most collectors find the spots unattractive but only up to a point. I think the word "greatly" is pushing the case too far. Having said that, all collectors are not the same: Some will happily accept these coins and some will absolutely reject them and there are many in between those extremes. Also, spots on a coin that is really rare is considerably different than spots on a common coin. Most of the time, spots such as you have shown are merely a place where the toning/corrosion that affects all coins has progressed differently than the rest of the coin.
Here's another example where the spot crossing the cap, LIBERTY and into the curls did not affect the grading. This 1835 half cent is from my type set. NGC AU-58. But it's the only spot on the coin and doesn't detract much at all from the eye appeal. If there were multiple spots it is likely that the graders would have knocked it down to AU-55 or lower.
