Interesting page David. I've come across a few of these pianos under various names and they're all pretty awful to play! These baby grands are one instance where I'd recommend someone buys a good digital instead of working on one of these.
Some technicians try to say the Blüthner patent is a D-type, but of course it's not. It's not quite a double escapement but it does have good repetition once you know where the point of sound is. Point of sound is a pianists term for where in the key travel the sound happens, I don't remember the equivalent technicians term.
No indeed, the Bluthner Patent Action is a different thing altogther! I was contemplating a page about that too, or about Bluthner more generally.
Dr. Brian Capleton in "Piano Action Regulating" says on p95, of the D-Type Spring & Loop Action "The action is as much capable of sensitive repetition as the roller action, when it is well regulated". Well, I don't see how that can be! It has half the components! And in most of the nasty little pianos you find them in, the age is such that felt and leather parts are worn and moth-eaten, and the action not CAPABLE of well-regulation.