IIRC, back on the old Jouster forum there was a lengthy discussion about such cartouches and the phrase was coined by someone describing them as "ink stamp cartouches". As to the how was covered above by Rick B and Red. Anyway, about one month after the discussion, another member reported that he'd just observed several "fresh" ink stamp cartouches on stocks offered at a local gun show. Close inspection showed that they were indeed "ink stamps". Just goes to show the fakers pay attention to what we post.
"No man's life, liberty, or property is safe, while Congress is in session." Mark Twain