I did not notice the clear-coat over-spray on the driver side mirror until 3 days ago. It only showed up when the sun hit it and then it was glaring. I decided I would clean it like I had the over-spray on the windshield. WRONG! I scratched it. Not much, but scattered all over the mirror.
I called Muth. The mirror is glass, but it has a coating on it, and if you try to buff the scratch out you go through the coating and you can see through it.
Long story short, Muth told me to send it to them, they would try to replace the glass, if successful it would only cost $40 plus freight. Other wise they would sell me a replacement for about $100. I sent it today, I will let you know how it turns out, he said about a 5 day turn around.
Be careful when you clean these mirrors