Re: Where are the oldest aikido dojos in the world?
Until a recently I'd been working on a research project locating old dojos. I have obtained a fairly large list of Budo Senyokai branch dojo locations from 1932 to 1933 that I've compiled from issues of their hard to find monthly newsletter "Budo". Along with the prefectures and addresses there are listings for dojo cho for each branch. I was planning to do a comparison of earliest known Aikikai branch dojos, but regular life got in the way and so onto the back burner that went.
The one that jumps out to me was Budo Senyokai shibu dojo 39, located in Iwama machi. Stan Pranin mentioned somewhere in his vast research that there was a Senyokai dojo in Iwama in the 1930s, but I don't think he had information on their shibu dojo number system. I now have four or five issues of "Budo", and each issue published a list of newly added branches and their dojo chos. I believe that it went up to at least 120 or so branches.
Somewhere along the line "Budo" ceased publication and was replaced by another monthly called "Kobu". I've tracked down three issues of that, but I don't recall offhand if they had a shibu dojo system like the Budo Senyokai. It seems possible that some of these locations may still be standing today.