Real Or Created Rainbow Toning On Proof Lincoln Cents?

Mr. Frog.

Altered toning, ok got that. But on the subject of certification does the TPG grader have some insight to the coin others are not privy too when they grade? This particular example grades Proof 67 RB PCGS with no QA or CAC sticker but also no Questionable designation either.
Other than instinct, experience and guesswork how would the individual or grader know unless it was actually busted out of a mint case? As my questions are somewhat obvious to my own answers which are "we, they don't" I go back too the premise of stay away from these coins, risky, not worth much more than normal, eye candy etc. After a couple hours self research I see only one trend that being; RB coins seem to command higher premium than Red examples. This particular coin has a slash mark in lieu of $ value in the PCGS price/pop report. Like anything I understand these coins are subjective but I find myself admiring them. Some of the high end sets proudly display these rascals, so again the question comes up about authenticity, premium etc. Risk vs reward, got that. I'm shying away from these things unless their in original mint holder.

Buy the coin, not the holder. PCGS should have definitely put that in a PR details - Questionable Color holder.

Cammy, why do you want to buy a damaged coin?. I ask in all seriousness tho. I believe even a natural progression of metal discolorazation to be a deterioration of metallic state content of a coin. "Rainbowing" is the first stage of "tarnish" of which Grandma had a fix....this "patina" is the first stage of a "metal rust" for lack of better adjective, to describe metal oxides happening, the crusty, black scale that happens on large coins, or carbon flashing. Unless arrested in progression, this will deteriorate into the lesser states. It may look nice now, by in 20-30 years, won't.

Naturally toned? Do events in nature produce perfect results? 'Nuff said. What caused it? A round object like a socket was centered on coin, something sprayed/wiped/brushed around it. (Lemon juice?) This would give a variance up to sharp division line.

Never seen in any mint holders I've purchased or even looked at, so suspect an implant is in one. Only coin I will say I've ever seen verifiably naturally rainbow toned was found in a repackaged snap cased 2000 ASE, but sure wasn't a perfect center or circumference. Since my personal preference was to dip it, I decided to show here on CCF first, snatched up and saved from my fire real quick!

Note the one in the middle:

The toning on your coin is 100% mint natural and market acceptable. The 1970S proofs are well known for toning in the mint packaging. I've owned many of these rainbow toned 1970S's - several in PCGS and NGC slabs.

Here's my PCGS MS-67:

I've owned quite a few of these, I love 'em!

The 1970S proof cents are very, very well known for developing rainbow toning - over 20 years now.

I standby my opinion that there is no such thing as "artificial" or "natural" toning. It's hogwash. A coin is either market acceptable or it is not. Yes, people "create" toning - but, just like cleaning, when it's done right the coin can be market acceptable. That said, more often than not, such experiments end in a complete disaster ruining the coin forever.