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<p>[QUOTE=&quot;Oldhoopster, post: 2732726, member: 84179&quot;]No idea if this is correct, but here is a possible explanation on why the coin has the black level of dark toning for over 50 years.&nbsp; Toning is caused by the silver atoms on the surface of the coin reacting to other elements such as oxygen and particularly sulfur (simplified explanation).&nbsp; The speed of the reaction will depend on the environment and concentration of the contaminant.&nbsp; As the sulfide layer gets thicker the color will turn darker.&nbsp; Over time, there is less “fresh” silver left to react and it takes longer for the sulfur to penetrate through the toning layer.&nbsp; At some point, the toning will slow as the coin darkens. </p><p><br /></p><p><br /></p><p>If the coin was exposed to a highly concentrated sulfur environment as it sat at the end of a coin roll, the exposed surfaces could tone very rapidly.&nbsp; Once removed from this environment and placed in the display, toning would slow.&nbsp; The newly exposed fresh surfaces would tone over time, but the dark area, with the thick sulfide layer would not appear to get much darker.</p><p><br /></p><p><br /></p><p>Once again, it’s unlikely that the actual cause can be determined but it’s interesting to speculate and I think this explanation may be a good possibility.[/QUOTE]</p><p><br /></p>

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