How does a coin get toned like this?

DesertLizard

Since toning is everyone's favorite topic lately I thought I would ask about these coins. I am new to toned coins so bear with me.

1] How does a coin tone like this?
2]Is it unusual for 2 coins to tone very similarly assuming they were stored apart, or is it like a fingerprint where no two are alike?
3] Could this be a AT coin?

Interestingly, the 2 coins are both 1921 Peace $ and at first I thought they were the same. Under further inspection I see they are not but the toning pattern is so similar I thought maybe there was a bit more to it than coincidence.

airplanenut

A lot of albums/storage envelopes had such things as sulfur which tones coins- the monster-toned morgans tend to come from the bags they were in for so many years... those both look natural... and pretty

dorkkarl

the first image looked like the start of stupendous wayte-raymond toning. if left alone in its album for a couple of decades, might turn into something extremely special. the second pic, i think a smaller coin was laying on top of the dollar for a long time, allowing the exposed area to tone.

K S

nwcs

The toning, to my eyes on the pics, is genuine. Most likely caused by being in a paper holder of some kind for a while (but not directly touching it) and then moved to another holder which kept it from continuing to tone. The first one almost looks like it was displayed on a cardboard tube.

GP

Looks like the beginiing of tab toning, and the coin was turned a little at east once. Then again, I could be wrong, but thats my initial thought.
The toning "center" is almost a perfect circle, and the turning of the coin would cover over the exteded part of the tab.