Scott US #634 (Used) Orange Corner Color Error

I found this Scott US #634 with what appears to be orange ink in top right corner. Ink appears to be present and of a different color rather than just being thin; however, I might just be unfamiliar with common print/ink issues…

This was one of the thousand A157s I'm sorting through, so variants have become quite interesting to me. I haven't come across anything but used 11 x 10 1/2 yet. Opinions welcomed. Thanks!

It's just environmental damage, caused by sun, snow, water etc.

It could also be from a chemical spill from things like cleaning solvents or even food.

Looking at the scan (or at the stamp through a 10x magnifier) you can see there is a wearing away of the printed lines in the corner. Clearly, something has affected the ink rather than the ink being printed in a different color.

@Ciletaliph @hy-brasil Thanks for the comments! I see now what you're saying—makes sense.