Considering how many "rainbow" toned AT coin I see in PCGS holders, it may not matter. One common Morgan graded MS62 in a PCGS holder sold for over $1500 on ebay the other night that looked definitely AT to me, I have never seen unnaturally bright colors on any other coins but Morgans and Peace dollars. If bright garish colors were on Seated or Trade dollars submitted for grading they would come back as AT.
Usually an AT Morgan Dollar has rainbow toning, or at least attractive toning. The toning on that coin is neither rainbow nor attractive. It looks to me like a secondary toning that formed after a dipping. I think the best course of action would be to dip the coin again. Furthermore, the coin has the appearance that it is lightly circulated and lightly cleaned but it is tough to tell from those photos. To my eye, this coin has no numismatic value, only intrinsic value.
I have a coin that sat in a small paper envelop for about 30 years and it turned it very dark like that and graded fine.
I would strongly suggest that this particular coin is natural. Just from the way it is embedded in the luster to me is a good sign it is nt. although there are some who are very good at what they do and can simulate toning so well it is hard or even impossible to tell by eye
