We're off topic here, but that story sounds a bit strange to me. If the rank you're referring to is Aikikai (I suppose Shioda was of high Aikikai rank before he left) were there really formal grading tests on that level? And including weapons, even more surprising.
If the rank is Yoshinkan the story also sounds weird. The founder of a style getting rank in his own style, judged by whom?
It was 1951 in Iwama, and the uke for the test was...Morihei Ueshiba. I suppose that makes it Aikikai
The first part of the test was sword, the second part was empty hand.
Actually, Shioda never left, since the Yoshinkan never formally separated from the Aikikai - they just sort of developed in parallel after the war. I don't know how it is now, but I believe that Shioda was on the board of directors of the Aikikai until he died, and vice-verse with Kisshomaru and the Yoshinkan.