It was surely not called Trabant, as that always was the name of a car model, not of the factory. The manufacturing company was the former Audi factory, by then called AWZ (Automobilwerke Zwickau). In 1958, it was merged with the former Horch factory, the Sachsenring Kraftfahrzeug- und Motorenwerke, to become the VEB Sachsenring Automobilwerke Zwickau. So you might call it a Sachsenring P70 Coupé prototype. The photo isn't good enough to identify the logo. It certainly isn't the AWZ logo anymore, but I'm not sure whether it really is the Sachsenring-S.