I have sincere doubts about the year. I know your source where 1956 is mentioned, but the first of five P50 sedan prototypes was built in October 1956. And that car was still to be changed slightly for production which started in 1958. I know a P50 Coupé design proposal by KWD from August 1957 which still had a roof shaped like the one of the P70 Coupé. A P50 Coupé body with the looks of the puzzle model was built in 1958 by KWD, after a similar design was drawn by the designer Rosenzweig from Karosseriewerke Halle in November 1957 (see below).