I recently removed the aio unit and replaced it with a previously owned kraken kit from an old card. ( I did this because of noise issues, but this is not about that topic.) As I was cleaning the paste off the aio from the new card I noticed something strange. It is not dirt, and when I zoom in some spots appear to be micro pits. I don't want to speculated what it may be as to not guess at something more serious than it may not be. Just want it to be seen.

I cropped the original image and decreased brightness so it was easier to see.

https://imgur.com/a/bAPSBpy

(Original) https://imgur.com/a/sJgs0wF

I can guarantee you that none of it is dirt, or otherwise anything on the plate that is higher than the plate itself. I have a certain type of OCD, and even though I was not planning to reuse the aio I HAD to make sure it was clean. So I thoroughly cleaned it with a soft cloth and plenty of 91% alcohol. Until the cloth no longer picked up any residue, and the surface was smooth. As smooth as could be for the type of milling that was done here. The only thing that can be felt is the very fine ridges from the milling work.

I will attach three new photos of the best I could get from my phone. I cannot do any better.

Angled, no detail. https://imgur.com/a/TocDH8q

Straight on, with milling visible. https://imgur.com/a/ebdq56J

Slight angle that matches and shows more detail from the previously thought of "discoloration" https://imgur.com/a/UvN0L2r

It is very hard to get a good shot. Not just because of my limit means, but because of it being so reflective. The surface is smooth in the sense that nothing can be felt protruding above the surface, however the surface itself is a very fine series of milling ridges. If you ran your finger nail across it then it would sound a lot like a zipper.