Hi, What are the typical ways that single-sided toning develops? I recently purchased an UNC silver coin that has some light toning around the edge on the obverse, but the reverse is uniformly darker in tone. Is this a possible indication that it has been sitting on a collector's display shelf or something similar? What are some of the ways that this type of toning could occur? Thanks
I have found two main ways, from what I have purchased. First is end of roll toning, where the roll end is not tight and the last coin gets toned on one side. Second is album toning, where the coin is placed in an album. Album toning can go both ways, actually. I have seen some where the facing side was toned, but the back was blast white, (good way), or the "bad way" is the front was a little toned and the back deeply toned, (corroded). I believe this second type occurs in too humid of conditions, where the album soak up the water and the front can dry off but the reverse is continuously exposed to moisture. Those are the main types of one sided toning I have personally purchased "original" coins. Chris
As coins don't naturally sit on their edge, it may be possible that one of the sides that was less exposed toned more. This is more likely on coins that sat out than album toned coins, because in an album both sides may or may not be exposed to equal amounts of sulfur. On a single side toned coin, the exposed side may have more equal exposure to sulfur and air. The toning may not start on the unexposed side until the toning spreads around the rim and to the other side. coins in rolls with other silver coins may not tone as much, but the end coin may.
Its rare but if a coin was to lay on a piece of paper for a very long time without been moved. It would also tone only on one side, but most of the times its because it was stuck in an album. Another way would be if the coin was in one of those government issued bags and one side got pushed up against the canvas, like Morgans.
When I started collecting it was a "given" that coins almost always toned on just one side and two sided toned coins with similar toning on both sides were looked on with suspicion. The only exception being those coins that showed the concentric toning common to coins that had been in Wayte Raymond folders for years. Coins tended to tone in cabinets where they lay flat where one side toned and the other didn't, or in rolls were the end coins toned on the exposed side, or in bags where the side or edge closer to the bag toned. You could see some two sided envelope toning, but it wasn't as common as single side toning. Today two sided toning seems to be commonly encountered.
Single sided toning is also extremely common on silver dollars that had been in bags for years. The side next to the bag would tone in bright colors; the side opposite would remain white. This is a textbook example of a GSA dollar toned on one side: http://coins.ha.com/c/item.zx?saleNo=1169&lotIdNo=40209
As an example of the paper situation described above, the coin below, sat in a plastic baggie with a business card on it.
Sometimes the album side just destroys the poor reverse: I have a whitman where the reverse of 25 of the dimes look like this. What a shame Oh the humanity!!!!!
