Pisiti, You can see in Don's method that using something like photo shop, with an image, even without a perforation gauge (odontometer), the pers are the same all around. So it can only be all perf 11 or all perf 12.
Your "discovery" of an "unlisted" item is actually the discovery that you've either read the gauge wrong, or used the gauge wrong. It's not an indication that you've found something unlisted. One should ALWAYS be weary that "not finding it in the catalog" probably means some level of misidentificaton somewhere. Double, triple, check all the facts first. Try to prove what you have and what you know, not what you don't.