Originally posted by Mistral75 + a nod to the MR-52 / MZ-D prototype or rather its successor the K-1 (which was publicly shown in 2011), a MZ-D shell covering the 24x36 prototype camera deriving from K-7 on which Pentax was working in 2008-2009 in parallel with a medium format prototype camera with a 33x44mm sensor which eventually became the 645D.
Interesting, it's the first time I hear that this K-1 is not the same old prototype shown since the beginning of the years 2000. So it was all true, Pentax had been working on a 24x36 digital camera for a long time.
I am a bit sad that no picture taken with this camera has been released.