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<p>[QUOTE=&quot;SuperDave, post: 2812472, member: 1892&quot;]The Morgans you present here look to have some form of silver sulfide toning. Not the prettiest examples we&#039;ve seen, but I wouldn&#039;t expect acetone to have any effect on them whatsoever. It&#039;s not &quot;crud,&quot; it&#039;s &quot;tarnish.&quot; As such, only those processes which either remove or reverse the chemical reaction which has occurred will help them. Thiourea (&quot;dip&quot;) will strip the tarnish, but you run the risk of removing too much and leaving a plainly-overdipped coin which won&#039;t ever look original again. There&#039;s a point past which the layer of tarnish has become so thick - usually identifiable by the dark color present - that you have to remove too much metal for the coin to recover. The patch on the bottom left of the reverse of your first coin is an example.</p><p><br /></p><p>Given how they were stored, it&#039;s possible that PVC was not the culprit for the Peace Dollar, and there might be other chemicals which, um, added their thoughts to the tarnishing process. </p><p><br /></p><p>The hardest part of conserving a coin is deciding whether conservation is possible or recommended. We had a recent thread here where NCS truly screwed up a coin; frankly, I don&#039;t think that coin was a candidate for conservation and they should have refused the job. The proof is in the results they obtained. </p><p><br /></p><p>These Morgans are, to me, borderline. One shouldn&#039;t attempt conservation for coins of less than high AU grade - except in cases of dire need to avoid active PVC or similar - because conservation is kind of all-or-nothing and the resulting surface cleanliness is incompatible with &quot;originality&quot; at a circulated grade. There Morgans look to likely be Mint State or, at worst, very lightly circulated and as such qualify on that basis. The covering is pretty thick in places, though, and one is left wondering whether an intervention comprehensive enough to remove all of that might be overdoing it.</p><p><br /></p><p>I hesitate to recommend a process because the goal is to retain originality and pleasing appearance, and most of these processes are not to be undertaken without enough experience (spell: &quot;enough coins ruined so you know what going too far looks like&quot;) to approach things confidently.[/QUOTE]</p><p><br /></p>

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