The top time only (there was a repeater and other very specials) are the Dietrich Gruen, 50th anniversary, and the Maadresch made movements. I have had a couple of those that were made by Assmann in large size but am curious about the small size version that is similar to the 50th Ann. except the movement is brass rather than the solid 12k gold of the 50th.
I wonder if I am right in considering the brass mvmt. as rare as the other top production models? I have seen more of the Dietrich and 50th for sale. Maybe it is the rarest?