I'm thinking NT. Both sides have a soft natural look to them. The colors are not bright and bold but appealing.
It does not matter because AT or NT, this color and pattern is what people like and there are a lot of them around.
Natural, probably from several decades in an album. If it was dipped, that would have been a while back.
@physics-fan3.14, I have copied the obverse photo below with some circles. Are these the splotches being referred to? If not, what is the diagnostic that indicates an old dip and natural retoning? Not a challenge, I simply don't know.
It has some nice album toning after a dip long ago. It's what the late Boston coin dealer, Don Romano, called "original now." There is nothing wrong with it, and I find it attractive. I hope that it has formed over a period of years. If it's happened in the last 6 months, which probably not the case, you will need to look into neutralizing it. Attractively toned silver is nice. Black silver is not.
For sure, can’t win every round when you’re fighting a proof. Personally I like fully struck centrils whenever possible on these but especially on proofs... just feels like they should be there.
Those are a couple of them, but its far more extensive than that. Look at the toning above her foot. Around star 1. Around the top of her head. Around all of the right side stars. The toning isn't "smooth." It's splotchy and speckled. This can be a natural look, but usually it implies to me that its retoning after a coin was dipped.
What are the chances that a coin from that era would remain bright white and then attain ring toning? Clearly had a bath and then retoned, probably in a Wayte Raymond album or something similar. "original now," as JM said. I have also taken bright white, dipped and cleaned coins that I purchased in my early young &dumb days, put them away in brown paper and they attained similar hues of toning.