Regarding the issue of patina and to clean or not to clean, I am in agreement also. If a coins is of obvious age and value, I wouldn't overly clean it. Leaving it in it's natural aged patina is best. The coins I referred to were coins that were so bad that I felt that they couldn't be spent or put back into cirulation. I don't know how they got that way but it seems some had gotten wet at one time. A few were kind of stuck together with a greenish pasty corrosion or something. Incidentally, they were all pennies except for 2 dimes. All were, what appeared to be, modern clad. One coin turned out to be an early 60s penny but when I put it in the Barkeepers Friend, it was so bad I couldnt decern the date. All I saw was part of the Lincoln Memorial on the back. When I took all the coins out and rinsed them, I set them on the table and it stood out among the brighter higher polished looking newer coins. It was a softer finish and a deeper or richer color but clean as new. I looked at it through a lupe and saw the date. I would agree, that coin would have been better kept in a dark brown color. However, choice being crusted over, unreadable and green corrosion all over it, or shiny, I guess shiny is better.
The suggestions I have made definately apply to common coins that are being cleaned for reuse in spending. Not something I would do with a candidate for a collection.
