But as it was mentioned earlier...being able to trace the authenticity of an instructor is difficult these days. Documents can be forged etc.
This is the age of digital cameras and youtube.
It would be highly unlikely that someone who is teaching hasnt had their stuff videotaped, (i.e. seminars,test, etc.), and/or have pictures of them in their 'aikido milieu' with their teachers, etc.
Dan grades are tracked by Hombu, so even that is pretty straight forward.
Again, do you vibe with the instructor is the point really.
Suppose you could find a black belt, that is totally cool in their technique - but just doesnt know how to relate...not everyone is cut out to teach - its actually quite tricky...and even then, people are drawn to various teaching styles.
So when it comes down to it, papers aside, the person will be drawn to what is needed for them at that time.