Morgan Dollar at 140X bid!

Supposedly once you remove the source causing the toning (e.g., sulpher) and seal the coin in a slab the toning should stop. Time will tell.

 

Log in or Sign up to hide this ad.

I am not that concerned about the coin turning inside the holder, but if you were you could keep the slabbed coin in an intercept shield holder and replace the holder every 10 years.

I have had some toned coins for over 10 years and they look identical to the day I bought them. Keep in a cool dry place and everything should be fine.