Sounds like you are referring to Seichii Sugano Shihan's 5 paired bokken exercises--ichi no ken through go no ken, which were taught widely by Sugano in Australia, and I think are still taught widely in Australia by his son, I think his name is Jikou?
We are doing a lot of work on these right now at NY Aikikai as Sugano Shihan recently passed away and left very little by way of videotape of this legacy. Here is one video that gives a bit of information. Toward the end he goes over some of the paired exercises that make up the ken series:
They're amazing exercises, not the same as suburi or kumitage because while they are somewhat scripted, they depend much more on reaction and relationship than form. Sugano talks in the youtube clip about "feeling pressure on your body" and forcing movement in the exercise by breaking maai rather than starting because nage has signaled readiness by presenting an opening. This emphasis on forcing and reacting is quite strong, and in my limited experience somewhat unique. It's been positively affecting my training.