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<p>[QUOTE=&quot;Tamaracian, post: 8388088, member: 23122&quot;][USER=81795]@Dynoking[/USER] there is NO guarantee that any slabbed coin will not continue to tone--to a degree--from what it appeared to the unaided eye at the time of encapsulation, however, there are many silver alloy coins (I&#039;ll focus on these for now) in old holders that were &quot;white&quot; when slabbed, or that had some degree of toning that would be considered non-terminal (i.e. not Glossy Black or Dull Black per <span style="color: #0000b3">Sunnywood&#039;s Color Classification System for Toned Coins</span>) that were stored in &quot;favorable&quot; conditions and <i>did not</i> progress to the Terminal Stage.&nbsp; Slabbing a coin in the more modern Holders where the Plastic used for the Case; the Insert used to hold the coin in place; and the Label were all of non-outgassing materials significantly reduces or eliminates the Holder from contributing to any potential toning (the top tier TPGs use a controlled atmosphere where the coin is slabbed), however, although the atmosphere surrounding the coin is only only a few cubic centimeters in volume, the ultrasonic seal is often not perfect (i.e. not hermetically sealed) and gas can permeate somewhere along the Seal.&nbsp; An example of this would be in storage where the ambient temperature changed in big swings, and there was high humidity or sulfurous gas present; the internal atmosphere of the Slab could be partially expelled during exposure to warm temperature, and when the ambient air cooled, a partial vacuum would be created, sucking in a small amount the local atmosphere; a repeat of this cycle would generally result in some toning over time</p><p>.</p><p>If a Slab is stored in controlled conditions (e.g. an AC environment where the humidity was kept below 60%) and there was no material in close proximity that could outgas (e.g. normal paper products), then you shouldn&#039;t see any perceptible toning, or toning progression (i.e. darker color or change in color) over time.&nbsp; </p><p><b><br /></b></p><p><b>NOTE:</b> we have to exclude coins that were treated chemically (e.g. dipped) where the chemical agent was not completely rinsed off; also, dipping a coin until all traces of previous toning have been removed--and especially re-dipping or exposure to the Dip for too long a period of time--will result in random, uneven surface erosion, creating pits and fissures that increases the overall surface area; while this coin may remain bright in ideal storage conditions, it will generally start to tone (a light gold) over time, and further progress if not stored ideally, whether kept Raw or Slabbed. </p><p><br /></p><p>A discussion of Toning due to Thin Film Interference, and the Toning Progression Spectrum, can be found at this Link:</p><p><span style="color: #0000ff"><a href="http://www.jhonecash.com/research/sunnywood_classification.asp" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.jhonecash.com/research/sunnywood_classification.asp" rel="nofollow">http://www.jhonecash.com/research/sunnywood_classification.asp</a></span>[/QUOTE]</p><p><br /></p>

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