Thanks to Derek Chapman for his data. It is interesting that Wille was in Hannover; Wagner in Braunschweig, and Gundermann & Kornacker in Magdeburg. These are all no. German makers of a kind, and all somewhat close to each other geographically. That is, as you travel from east to west on the A2 from Berlin to the Ruhr (or vice versa...), you pass through each of these towns. I had not known of the cap makers, heretofore, save from C. Wagner. I am also sure that I have left something out in my little compendium, as well. However, Kevin's Gundermann & Kornacker tag is quite a welcome addition.
