It is a DKW F91 sports coupe, built by Belgian coachbuilder D'Ieteren in 1954 for Edouard Boucquey. The body was made of aluminium.
In 1955 Boucquey took part in various rallies with it, including Liège-Rome-Liège (3rd place, see puzzle photo), Circuit Nivelles (3rd place overall, class winner 1000 cc).
There are said to have been contacts with the developers of the DKW Monza.