Hello, I couldn't find anything on this topic in these forums... I'm using three different vintage Pelikan 400s (one of the "original" series and two of the 400nn series). I have noticed that the number of stripes may vary. For example, the original seires' 400 and a green striped 400nn have 24 stripes on the barrel, whereas the other 400nn (pictured left) has 30 stripes: I know celluloid patterns are supposed to vary, yet a clear difference in engineering and design can be seen in the image. Is there a known history of barrel design for the vintage 400 models (1951 - 1964)? I know these barrels were made from acrylic plastic on the inside and celluloid on the outside. I suspect there must be a history of design and engineering changes, which can help in dating the pens more precisely. I've searched the web as well as printed documents within my reach, yet couldn't find anything on this topic. Any information would be highly appreciated. Thanks in advance! Regards, Stoen