O.K., and another thing I'm gonna throw out there, and have never seen mentioned before, is the fact that a nearly uncirculated or uncirculated copper coins tend to exit the ground in pretty nice shape while worn coppers seem to degrade much quicker.
My theory: Original mint luster on a coin is actually raised metal occurring in the minting process. Luster wears away very quickly leaving just the base metal of the coin, which would seemingly be much more susceptible to true corrosion.
Luster, in my opinion, somehow saves the coin somewhat, as a "buffer" so to speak, therefore allowing a nearly or uncirculated coin from incurring initial damage when dropped.
Just a thought, would like to hear comments!
Greg