Peter A Goldsbury
If it is the same technique (and I am used to the pinning with the leg version, but it depends on what you do it from), I first saw it used by Rinjiro Shirata here in Japan, who talked about such techniques being "prewar". Everything that Dan states, including the difficulty of pulling it off with a non-cooperative uke, rings true from my own experience. However, I know that Arikawa Sensei was a good friend of Katsuyuki Kondo and used to watch his training, but he (Arikawa) once stated to me that he had not actually trained in DR.
I am sure the provenance is DR, but I also believe that much of what would nowadays be more strictly DR was practised in aikido dojos and it was only with the emphasis on kihon techniques, with the ambiguity implied by this term, that this other stuff was lost. Well, it is not completely lost, since it is still practised in some aikido dojos.
I just noticed this thread and post, so I'm a little late.
Yes, indeed, Shirata sensei both demonstrated and taught this kind of pin. There is a whole variety of them actually. In my experience the difficulty isn't so much in applying the pin on an uncooperative opponent (Does one call a cooperative
partner an opponent?). Rather, it is getting to the point where one can effectively apply the pin that is the "Art" proper. Kind of like tachi dori, it is surviving and gaining control over the initial threshold interval that is the hard part, what comes afterwards is relatively easy. Get through that and one can choose to dispatch in time, dispatch upon consolidation, or bind (pin, tie). With a cooperative "opponent" this gets all turned around on its head and one is left entraining themselves with human macramé. Or, I'm guessing in the cases of accomplished "masters," one might amuse themselves with the "macramé' aspect when the opening interval becomes old hat . . . I wouldn't know.
Dan's comment about sealing the breath is interesting. I don't know that I can replicate this with this type of pin. I've never really paid attention to that. When it was applied to me the experience was so all consuming that I don't think I gave it much thought and rather went for the "all consuming" aspect when trying to replicate the pin myself. It is interesting to think about what discreet elements combine to constitute that affective experience. Hmmm . . .
Specifically with this pin, not necessarily with others BTW, I've always thought about it in terms of skeletal (tendons and ligaments in so far as then apply to the skeleton) mechanics. I never really considered applying Kokyu Ryoku in any specific way as I would in say an Ikkyo pin (which I consider a transitional pin BTW.)
This is interesting to me. But I gotta go. Maybe one of you will see this and pick the thread back up.