What Kind Of Toning Might This Be?

TL;DR I am trying to determine if the toning on this slabbed 5 Pesos is "natural" or is toning/staining around residue from an old dipping.

This was a recent ebay pick-up. I'm pretty new to Mexican coinage and I was specifically looking for an example that wasn't blast white. I'm sure it's not to everyone's taste, but I like the look of the coin, toning and all, but basically I was suddenly hit by a concern over whether it's "natural" toning or connected to some past doctoring.

The surfaces look original to me, and it's in one of those older, white ANACS slabs (MS-63), but I remembered seeing a couple old threads referencing a kind of staining or toning that occurs after a while on coins that have been dipped and poorly rinsed, and since I don't have much experience with dipping or with looking out for that sort of thing, I wanted to see what the community here might have to say.

There are a good number of spots throughout the fields, some patterns that almost look like fingerprints, but I don't think are, especially around the edge, and in a few places there are some pretty subdued rainbow-y colors, sort of dark teal and purplish mostly. It has fairly strong luster.

So there you have it. Maybe I'm being paranoid. I like the coin, but I'm not massively experienced and I'd like to understand if this seems like a natural pattern of toning or not.