How to determine if Macbook Pro Retina anti-reflective coating is damaged and/or removed? (Preliminary remark: I'm not entirely sure if this type of question, about hardware damage, is encouraged on this SE site. Apologies if it doesn't belong here.)

The screen of my MBP Retina 13' (early 2015) started showing some odd 'stains' a few days ago, covering about 20% of the screen. Didn't think much about it, until I read about 'Staingate' later (silly name, but oh well).

Here's my problem/question:

I'm not sure if what I have is actually damage to the coating (i.e. 'staingate') or not.

On the one hand, the stains looked similar to those on the pictures people posted. 

However, before I read about the possible coating issue, I was able to remove these 'stains' with a soft, clean microfiber and some warm water. 
It took a while to completely do so, basically, rubbing persistently for a while, but without using force, just light pressure.

I am wondering now if (a) these were just regular (but rather persistent) stains, and I simply cleaned the screen, or (b) if I rubbed off what I thought were stains, but in reality, was some screen coating.

Is there any way I can determine this? 

For example, how would I be able to tell if my screen lacks the coating? Can you usually see your own reflection in a coated screen if the screen is turned off? I can do so now, but don't recall if that was always the case.

The machine is still under warranty, and if it is in fact screen damage, I will try to get it covered. But before going to the store, I was hoping I could first determine if it's worth/necessary to go there, hence, this question.
(disclaimer) I'm answering my own question, just in case someone else faces a similar problem, even though I realize the question itself maybe never really belonged on this site.



I had a chance to compare the screen of my Macbook Pro Retina with another (identical) model that does suffer from actual stains, i.e. partially removed anti-reflection coating.

The good news is that, apparently, I did in fact only 'rub off' some very solid dirt, that only looked like the 'stains' that some people see on their damaged screens.

How do I know the other one had a damaged screen?

When I cleaned my screen, I removed some 'silvery' stains, revealing a dark, almost totally black color of the screen/glass. In the case of the other, damaged Macbook screen, the opposite was the case: cleaning/rubbing seems to have removed the dark parts of the screen, and revealed the silvery stains.

How to tell if the coating has peeled off or not?

If you're unsure, the coating is (in all likelihood) still intact.
The silvery stains are very noticeable, and while I couldn't tell whether the other screen seemed more reflective or not, I could tell definitely that the stains are not even nearly dark in any way. In other words, when I removed the dirt (as I know now) from my screen, the resulting dark color of the screen when turned off, while not perfectly black perhaps, is drastically different from the damaged parts of the screen, which I can only describe as 'dirty grey/silver'.

Wasn't that kind of obvious in the first place?

Maybe. I'm a bit slow sometimes.