What can be done with coins that have came back as UNC Cleaned?

[coinman_23885]

10 years? The silver composition must really play a major roll in how quickly something will turn. I had a 1 oz bar sitting on my mom's picture frame in the living room. It is one of those Ten Commandments bars and her urn sits right there next to it as well. That bar, .999, was turning within a month.

 

I think jame's 10 yr mark was based around the coin gaining back some original patina and looking normal again. A cleaned coin can be toned very easily and quickly, but the damage is still visible.

 

Also, there is a huge difference in the toning rates and patterns of .900 coin silver (like this) and .999 fine silver. I think James_EaryUS is spot on in his estimate.