In 1965 the 850 was introduces during the Geneva salon d'Automobile. Swiss magazine "Automobil-Revue"devoted various articles to it in the salon catalog. A couple of photos:
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A few articles preceded that introduction, including a prototype. That started with a 600 with an extended rear:
A four-door version was also tried. Maybe for the Simca 1000?
Italian magazine Quattroruote published this idea in the February 1964 issue:
Close. But no cigar.