In TKA Nidan/Eedan is the last true test and Sandan/Samdan tests are the equivalent of being made in the mob. Third for us is probably the equivalent of 4th in other schools.. One of the markers of approaching this track is being able to teach other black belts. Also, the informal hieararchy sort of clues you into who is approaching the level. I'm sometimes hesitant to take the role of teacher at our workouts, but other times this comic shows how I feel about what people are doing or teaching. It's also very interesting when I have ideas that are at odds with some of the upper ranks in the school.
I think the interesting aspect of this process is when your martial knowledge outgrows your martial skill. Just knowing how good you want to be and knowing that you understand HOW to get there, but not yet being there... Man.