Look at this albino cut square. Pretty typical, no?
Now look at the back. Even the offset you see could be classified as mundane.
However, . . . A blue line has been placed just below what appears as a scratch.
It is interesting that there is no corresponding evidence of the scratch on the front. One would think that something mimicking an engraving event would be necessary for that image to show up on the back side of the envelope. Any ideas?
Edit: to use smaller sized pix.