I once saw a schematic presentation/drawing of the evolution of the shape of the dome of Prussian Officers helmets. I forgot where. The evolution...all in only one drawing. Perhaps there is an artist amongst the members/users here who gives it a try... Would be great. Is there a book/article that explains the different Models? That would be great. Thank you in advance. Have go through the good old J-L. Larcade Volume TWO again.