Yes I do have that book Oscar, and Zeiss did do some development of a Contax beyond the IIa and IIIa, but it was never really developed, even as a proto-type, in favor of pursuing the Contaflex and Contarex SLRs. Zeiss had patented a number of ideas and inovations throughout their history, and therefore had the technology to create many things ahead of their time. I believe they patented a coupled built-in meter in the 1930s for instance. In my eyes, they also did not manage themselves that well in the post war years. The design of the IIa and IIIa were clear advances over the II and III and at the time of their introduction they were the most expensive 35mm cameras on the market. That being said, they were "old fashioned" in design and function, something hammered home by the introduction of the M3 in 1954. Additionally, they faced strong competition from within their own house, the Contessa, Vito II and Prominent. Zeiss' reaction to the introduction of the M3 was a 100 DM decrease in the price of the Contax. Zeiss also apparently did not invest internally and upgrade their production facilities therefore their manufacturing cost were higher than Leitz's. Remember, their plants were more damaged than the Leitz plans in the war and their company was fractured with parts in West and East Germany. Ultimately it seems the choice was made to invest in the SLR systems instead of retooling and advancing the Contax RF.
All greatly paraphrased and borrowed by recolletion from Kuc.
