Those look like the kind of columns (early line arrays?) used to limit vertical dispersion in churches and gyms.
Anytime you put speaker in a vertical "line" you get the "line array" effect at some freq.
As you go up in freq you need to start using smaller and smaller drivers to get them to work decently.
This was described (as well as the lobing that occurs-and the manufacturers would like for you to forget), a couple of decades before this photo was taken.
Shure actually described the "effect" in ads for the "Vocal Master", and the narrowing of the pattern. I have some early ads that talk about it.
That is part of the reason that the 8" drivers in the vocal master were in the middle, and the 10" were on the top and bottom of the cabinet. Because the lower freq can be further apart to get the same "narrowing" as the higher freq.