We have a number of ACDs (aluminum) at work and all of them have what appears to be staining on the top of the display right under the white menu bar.
You can hardly see it when the menu bar is there, but as soon as you do something without the menu bar (full screen photoshop) you can see it.
All of the monitors were purchased at the same time and they all have this problem (total of 5) although some are worse than others.
I would be pissed if they were mine, however, when dealing with company property, as long as the display turns on, I guess it's okay 🙂 .