Tks Robert for your expertise for the possible presence of debris on the printing plate!
I also have another one in the same category, it looks like a fiber left this mark on an old 107, the fiber is not there and under high magnification, it looks more like surplus ink in a crack . I can not get a better picture with my scanner, so I used a macro lens through a magnifying loupe with side lighting.
I do not know how you can have the passiveness to scrutinize all your stamps as you do, me, I abound very quickly.
Paul.
