Lovely finds! I read this thread when it was fresh, and made note of the discussion of stitch watermarks. I came across on in the red box of revenues I picked up in Atlanta in Feb, but I couldn't recall where I filed it. I think my memory is going away.
Just ran across it again while checking that box for double transfers. The R18 is not all that great, but it is interesting never the less as it's the only revenue I have found with a stitch watermark. Haven't got the best photos, I hope you can see it.
So has anybody come to a conclusion of how prevalent these are?