Toned 1976 S Lincoln Cent

Please post a link to that info,I would like to read up on it.
John1

Me three! I really appreciate the info. I have been searching, but when you don't know what terms to query it makes it hard.

Is that a crack or scratch in the plastic next to the memorial where "UNITED" starts. It's strange that the bright red starts from there.

http://en.wikipedia.org/wiki/Proof_..._proof_coins (see "Production Process")
A lot of people have a bias against Wikipedia, so here is another one.
http://lynncoins.com/proofcoin_article.htm

The toning is a natural part of aging. Most likely it's due to the storage environment and the packaging materials. Gaseous substances like hydrogen sulfide react readily with metals to create a thin-film effect responsible for the color.

Welcome to CC!

I agree Thad, the mirrored section (the "field") is a result of the polished die. I misspoke when I referred to the mirror quality coming from the chemical, I meant the image itself. However I disagree about no chemical being used in the stamping process. The image portion of the die IS TREATED with acid to give the frosted appearance, as noted in the previous 2 articles.

Deep cameo's are a result of a newly used acid-treated coin die which gives more noticeable, frostier appearance. As the die is used over a longer period to strike a coin blank, the effect of the treated die fades which results to the less frosted look.  Proof coins with images that do not have matte characteristics are not designated as cameo.

Acid is NOT used during the stamping operation. The die devices are "treated" with acid to give the frosted effect and then moved into production. No chemicals come into contact with the planchets during coining.

Thank you for clarifying Thad. If I understand correctly, the chemical is applied pre-strike & then cleaned solely to give a portion of the die a rough texture. This effect is lessened as the die is used repeatedly, I assume due to the pressure of the contact with the planchet?

This would make a great deal of sense as I've read previously that sandblasting was used in the past, presumably to achieve a similar result.

I watched an informative video from the Discovery channel last night regarding the process @ what I assume is a Canadian facility. Very educational! I'll post that in a separate topic for others to enjoy. (See it here)