This is from interview with Morihiro Saito, Aiki News #88 ( http://www.takemusu.org/patsensei/ss/aj_91.doc
Was the present sanjuichi-jo (31-movement jo kata) finalized before O-Sensei's death?
Yes, by the time I learned it the kata was already complete, but when Koichi Tohei Sensei [presently head of Shinshin Toitsu Aikido] came to practice in Iwama it had not yet been perfected. What he learned was different from what I learned, probably because O-Sensei's way of instructing was not yet fully developed. When I learned under O-Sensei his teachings included all of the weapons techniques including the kumitachi. At one stage, there was no one left in Iwama except me, so I trained with O-Sensei by myself. His teaching gradually became more elaborate.
Did you teach the kumijo in Tokyo?
Not really, except to a few people in odd places such as on the rooftops of buildings. I used to teach the jo as a 27 or 28-movement form, but ended up with the 31-movement form as I found this was easier for students to understand. Just as my aikido has come to be called "Iwama-style," the "sanjuichi-jo" name that I gave to this kata has stuck.