Didn't Exakta make a version of that East German 6x6 SLR (the name escapes me right now), or did they just import the East German camera and spruce it up a little?
They made a Prewar and Post war 6x6 camera. They're both rare. I believe it was only about 2000 post war 6x6's that were produced, as they had a design flaw in them and were quickly discontinued. They fetch very decent cash on ebay.
The concept was refined and used for later 6x6 cameras (Kowa i think, but i could be wrong)