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<p>[QUOTE=&quot;calcol, post: 26193921, member: 77639&quot;]There was air in the tube when the coins first went in it. Also possible there were non-gaseous toning substances (sulfides/sulfites/sulfates) on the coins before they went in the tube.&nbsp; Tube may not be as airtight as you think.&nbsp; The plastic may be somewhat permeable.&nbsp; The plastic itself might generate toning gases, like hydrogen sulfide.</p><p><br /></p><p>Cal[/QUOTE]</p><p><br /></p>

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