Let me get a little scientific from my past stupid experiences. Magnesium sulfide (epsom salt, or palm tree fertilizer) burns white and sulfur is a known toning agent. So he treated it with a vaseline epsom salt paste (just a guess) then roasted it for an hour or so in an oven. (Just a theory)
He got over 250 bucks for a ruined cent, that makes me angry. I sent him a 'question' through ebay asking him what he coats his coins with.
In my opinion, the cent (proof or not) is just post mint damage. Sodium Hydroxide & Zinc dust can be heated with a cent to plate Zinc onto the cent. Here is a video describing the process. http://www.metacafe.com/watch/1262456/make_a_gold_penny/ Very best regards, collect89 P.S. I previously posted a brass colored specimen on CT & received this link from another CT member. P.P.S. Draino contains Sodium Hydroxide & the zinc source could be as simple as Zinc coated nails.
Just to clarify, after the current transactions are complete, he will have sold 3 white cents, all of which he has "never seen", and 8 blank back notes.
We have a resident chemist here, don't we? If I'm not mistaken, coin toning is simply oxidation. Wouldn't that produce a layer of Cu(2)O (the toning)? Then, if you dip this toned coin into concentrated Hydrochloric acid, you would have Cu(2)O + 2HCl --> 2CuCl + H(2)O? The CuCl (Copper Cloride) would be white? Nothing would have really been done to the surface, per se, except for this new converted layer of white CuCl that would possibly even give it the "orange peel" look previously alluded to? Inquiring minds want to know...