Help with glass!

[Shallow Planet]

I have this weird drip mark on outside of glass I cant get off. I tried vinegar for a few hours and it still sticks. I was able to scrub some off with a sponge but it scratched the tank so I stopped. I've tried a scraper with vinegar too but it also starts to scratch the tank. Idk what it is. Water drips just whip off. Not sure what this could be besides all, calcium, or magnesium from manual dosing.

Any ideas out there?

 

[motortrendz]

Is it glue? I use windex and a razor on my tank to clean it every once on a while

 

[Shallow Planet]

Couldn't tell you what it is. Dont know how glue would have gotten on it

 

[Shallow Planet]

When its wet I cant see it but as soon as glass dries there it is again.

 

[Bryson.bobby]

Did you try using a razor blade?

 

[Shallow Planet]

Yes. It at least the metal place from my mag cleaner