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<p>[QUOTE=&quot;calcol, post: 24554329, member: 77639&quot;]Sorry to hear about your coin.&nbsp;&nbsp; I had similar problems with my old Lincoln cent collection due to Whitman folders.&nbsp; Had to take to most of them to the bank … it was that bad.</p><p><br /></p><p>I agree with others that if it means a lot to you, send it to NCS.</p><p><br /></p><p>If you want to DIY, Coin Collections, Their Preservation, Classification and Presentation by David MacDowell, 1978, UNESCO, is a good reference.&nbsp; Based on this guide, the coin has spots of copper carbonate perhaps mixed with horn silver (silver chloride). Not likely to have much horn silver unless coin was in contact with soil or salt water although being toted in sweaty pockets over the years could do it too.&nbsp; A little salt spray could get the whole process going and account for the spotty nature of the corrosion as could random pockets of higher copper concentration in the planchet.</p><p><br /></p><p>Treatment is immersion in 5% formic acid until the action stops.&nbsp; Carbonate turns to carbon dioxide with bubbling in the presence of acid.&nbsp; The copper will become free ions dissolved in the liquid, which may turn bluish.&nbsp; Change the solution every 30 minutes if the action goes that long.&nbsp; Rinse with distilled water.&nbsp; Then a 30-minute soak in 15% ammonium thiosulfate to remove horn silver and silver sulfide.&nbsp; Rinse with distilled water.&nbsp; Above applies only to coins that are almost entirely silver.</p><p><br /></p><p>Don’t have formic acid or ammonium thiosulfate?&nbsp;&nbsp; They can be bought online.&nbsp; Substitutes are strong vinegar (acetic acid) and a commercial de-toning product (these have a thiosulfate salt in them).</p><p><br /></p><p>Cal[/QUOTE]</p><p><br /></p>

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