That toning looks perfectly natural to me. Looks like the sort of thing that a coin stored in an album would develop. Given that many people used albums, this is a fairly common type of toning.
It's possible. But it equally possible and I'd say likely even more possible that the toning is completely natural. Ya see, people selling coins are often selling their own collections, or collections they have purchased from others. And it's quite common for coins from any given collection to have similar toning on many of the coins in that specific collection. And since that toning looks perfectly natural to me, I strongly suspect it is. Uhhh, usually, MS70 will not remove natural toning, it's just not strong enough to do that. It will remove haze, which the very beginning stages of natural toning, but once toning has become established on a coin, it aint likely that MS70 is gonna take it off. No, once fingerprints are well established, acetone isn't going to remove them at all - even with a Q-tip. Fingerprints contain acid, and once a fingerprint has been on a coin for a while it actually eats down into the metal becoming permanently etched into the metal. And acetone won't even touch that ! The very most that acetone with a Q-tip will do is to remove some dirt that may be in the same area as the fingerprints. Now you can dip the coin with established fingerprints in a commercial coin dip, over-dip in fact, and that will remove the fingerprints. But even that will only do so because it is removing the metal to the depth of the fingerprint etching. And forever damaging the coin. Once you can see fingerprints on a coin, your best bet at that point is to just leave them alone. Because trying to remove them is going to harm the coin far, far more than leaving them alone will.
In a previous thread I demonstrated that an MS-70 bath followed by immediate acetone bath removed toning.
...and you barely have to touch a high luster surface to leave a print. This print was just from flipping. A sheet of wax paper over the subject enhances the contamination.
Yes, dramatically but what do you make of some some silver results. Was this dime not toned before the bath?
I would say no, but it was very dirty. And since MS70 is a detergent, it makes sense that it would take it off.
I think in my case what I was seeing on the coin may have also been grease left over from what was left on the coin from the fingerprint. It is mostly gone after dabbing the coin with the acetone and what I am now seeing is the damage done by the grease being on the coin.
So does toning require color? I also see this as some describe as "undesirable toning"? That coin lived in a zip lock bag with 2 other proofs for the last 20 years (see image). They all had the same appearance. I wouldn't think dirty, I would think patina.
A friend told me that if you ask three dealers a question about a coin, they will all agree, assuming two of them are dead. Everyone has an opinion, and without seeing the coin itself it is very hard to determine whether the toning is natural or artificial. Go on eBay and look at a group of coins, say toned Kennedy Halves, to my eye a large proportion of the graded coins that are toned look artificial. I finally, with the exception of ones that really appear to be artificial, the old frying pan trick, have given up and if the coin appeals to me I buy it, natural or not. Even the grading services, with their sniffer make mistakes. I recently opened up the box that a bank used when the ASE was introduced in 1986 and they gave them as a gift to regular customers. They had beautiful toning and when I brought them to my coin club meeting about half the members thought the toning was artificial. Speaking of mistakes by grading companies, I just received the Apollo 11 two coin half dollar set back that I sent to NGC. I'm a big Kennedy Collector and will buy, within reason, any new Kennedy coin. NGC reversed the labels on the two coins, labeling the Apollo 11 coin as the Kennedy and the Kennedy as the Apollo 11. That set will stay in my collection. The only thing that I know of that will remove toning without effecting the coins metal is acetone, just be careful of the fumes from it and give the coin a gentle washing and using a micro cloth, dab the coin dry.
Then we have different definitions of "toning". Acetone will remove many foreign materials from a coin's surface, but it won't do anything to the metal sulfides or oxides that form what the rest of us call "toning".
Toning is toning regardless of color, but yes, all toning has a color. The thing is the number of possible colors is the full color spectrum. As for the difference between toning and dirt & grime: toning is in the metal, meaning it doesn't wash off; dirt and grime is on the metal and it will wash off. Short and sweet toning is corrosion, it is the metal itself corroding, chemically changing from one substance to another substance. And all coins begin to tone the very moment they are struck. In point of fact the planchets were toning before the coin was ever struck. But by being struck fresh metal is exposed by metal flow and then that fresh metal begins to tone. And toning can never be stopped unless you can stop the metal from being exposed to air. Air, and what's in it, is what causes the metal to corrode, to tone. You can greatly slow down toning/corrosion by limiting the amount of air that can get to the coin, but you can't stop it because there's no such thing as an airtight coin holder. That said, yeah there are airtight containers that you can put a coin into and seal it up, and the coin will tone/corrode a little bit until the air inside the container is used up by the corrosion and once it is used up the toning will stop - until new, fresh air is introduced into the container by opening it.
Ziplock bags actually will inhibit toning - but inhibit means slow down, it does not mean stop. And Ziplocks slow down toning because they help limit (slow down) the amount of air that can get to a coin. BUT - plastics are air permeable, and Ziplocks are made of plastic. Air permeable means the air goes right through the surface of the plastic itself ! Tupperware containers are also very good to use for proper coin storage. But even they will not stop toning - but they will slow it down a lot ! I've written countless posts on proper coin storage, please do a search and read them.