The short-lived Free City of Danzig had at least one coachbuilder
The Free City of Danzig was created with the Treaty of Versailles in 1919. The Free City included the city of Danzig and other nearby towns, villages, and settlements that were primarily inhabited by Germans. As the Treaty stated, the region was to remain separated from post-World War I Germany (the Weimar Republic) and from the newly independent nation of the Second Polish Republic, though it had a customs union with the latter.
Nasza Historia, a Polish historical magazine featured a story on the history of motorisation in Danzig. According to this essay, there were over 400,000 people living in this area, mostly Germans. The car fleet consisted of 1620 passenger cars and 765 trucks in 1928
The article also briefly mentions Danziger Karrossiefabrik, but it mixes up historical facts. On another site, dealing with the history of Danzig there is a newspaper clipping which reveals the truth
Danziger Karosseriefabrik was set up in April, 1922 with participation from the Danziger Maschinenfabrik und Automobil Werkstätten Rendorff, Werner & Co (Machine Factory and Automobile Workshop of Rendorff, Werner & Co) in Zoppot and the Benz subsidiary in Danzig. The supervisory board consisted of a banker, a car dealer, representatives of the founding companies and the owner of a local carriage builder, Gebrüder Wendrowski, also in Zoppot.
Unfortunately we don’t know much about the activities of the company. Two photos of a 1928 Packard bodied by them and a photo of an unfinished car are in the archives of the National Archives in College Park, Maryland, DC, USA. This attracted the attention of Brooks T Brierley who in 1996 featured a short article in The Classic Car
Deutsche Fahrzeug Technik, a Germany magazine which featured hundreds of coachbuilders from the 1910s to the second world war had at least two bus bodies built in Danzig shown on their pages.
The company folded in 1931 and the factory ground was bought by Otto Binder.