Hückel Wien, measures 55cm. Hückel brand name but with Carl Kellner Hamburg sweatband. I have only seen the Hückel Wien designation used with WWI era hats. It has characteristics of an older hat but I think it's post WWII. The felt is really fantastic and it appears to have a silk liner which is also like no other Hückel I have encountered (pre WWII JHS, Hückel Tonak, Hückel Weilheim). I am thinking Weilheim probably early 1950s with special components for Carl Kellner Hamburg.
Update (11/29/16)! I found the following which might be the source of this hat.
"Der Neffe von Fritz Hückel, Hugo Augustin Hückel (1899–1947), der Sponsor des deutschen Raketenkonstrukteurs Johannes Winkler war, versuchte 1946 in Wien, zusammen mit der Hutfabrik A. Sindermann und P. & C. Habig als Hückel & Co. firmierend, eine Hutproduktion wieder in Gang zu setzen. The nephew of Fritz Hückel, Hugo Augustin Hückel (1899-1947) who was a sponsor of the German rocket technical designer Johannes Winkler tried in 1946 in Vienna, together with the hat factory A. Sindermann and P. and C. Habig as a Hückel und Co. firmierend to get going a hat production again."