Thanks to Heather's restoration job on the Japanese photos, I can see one of the gyros has a radial. It looks like a Wright, doesn't it? The other has the Argus, which is a 240-HP engine.
I bet you somewhere in Japan there's a memoir written by one of these gyro pilots. In the last few years Japanese veterans, just like Allied ones, have been wanting to tell their story before it's too late.
Chuck, I'm a history buff, so I really enjoy these postings of yours -- they're the next best thing to Dr. Bruce Charnov's articles in Rotorcraft. My undergraduate degree is in history, which qualified me for such things as Walmart greeter, kid who asks "would you like me to super-size that, sir?" "Would you like fries with that, Ma'am?", and combat infantryman.
cheers
-=K=-