alright this is within the past 18 minutes before and after. I'll pay attention and make sure I'm taking them from the same angle so we can really compare correctly. if it wasn't for these stains some of these coins have potential to get graded MS68 OR MS68+ in my opinion of course. no scratches whatsoever..
Enis, there's a lot being said in this short sentence - You see, what you're experiencing is nothing new, collectors have struggled with it, and endured it, for many decades. They've tried every trick that you can think of and whole lot more that you will never think of - to stop this from happening. Very rarely has there ever been any success. End result, most of them just give up trying as it is an effort in futility. And what very few successes there are, are really nothing more than accidents, a stroke of chance. But it is those very few strokes of chance that keep collectors doing what you are doing - buying those rolls. They all have dreams of success. But as a general rule the only successes every achieved are when the roll collectors re-sell those rolls intact. And that is the lesson, a lesson that only a few it seems ever learn because with every generation of collectors there are always those who do exactly what you have done. And only then do they learn it - and learn it the hard way.
Copper changes with age. There is no way to change that. You can slow it down a bit with proper storage but you can't stop it.
You have to realize the task you are facing. First of all old rolls of coins are in sulphur laden paper rolls. That right there is about as bad as you can get. Then, depending on the date of the coins, they might have already been in that roll for several decades before you ever owned them. For that matter, the coins may have been exposed to unfavorable conditions before they were ever put that paper roll. And that could have been not long after the coins were freshly minted, or even several decades after they were minted. The point is, it only takes a very short time for the coins to be exposed to something in the air. And then that "something" just sits there, on the coins, for decades. Add to that there could have been multiple owners of those rolls, all keeping and possibly exposing the coins to various conditions. So, no matter what you do in regards to storage, it's almost certainly already too late. It was probably too late long before you ever bought the rolls. As I said before, collectors have been trying to find a solution to this problem since about the 1940's. And to date, nobody's ever found a solution. Which of course is why they've given up trying.
The root cause of this problem is improper storage coupled with a very reactive substrate (Coin). The two constituents in the air causing this problem is chlorine and sulfur. The area you are probably storing these BU Cents is probably not always at room temperature and/or lacks a humidifier. We also know that zinc reacts more greatly with the above two constituents (Cl & S) than copper. I have developed a copper cleaner but its not cost effective for low end priced coppers of this type and it would not be cost effective. However I do notice some of these cents are of a high copper content and not copper plated zinc. Perhaps only the top two coins or so in each roll is environmentally damaged. Contact me privately if you wish to investigate your options further ... if the entire roll is spotted no need to reply ... of course. John Lorenzo Numismatist United States