Robert, here is a challanging one to find a counting mark on. It is the .57c sea otter / harbour porpoise issued May 13, 2010 jointly by Canada Post
and Sweeden. The booklets had panes of stamps with a one or a two on them, some with serial "'s also. It is difficult enough to find one that has a counting mark on, it let one that also has a 1 and a serial # printed on the upper booklet margin. "Booklets" has yet to locate one as of last year. I was fortunate to find two. As well the location of the couning mark can be lighter or darker, not extend completly around, and also be found in a variety of different locations and also multiple marks as can be seen in the image below.
The "puzzler" had a thread on scf on this particular booklet issue and a link is below the picture with a lot of data.