That is really cool. I didn't know that the design was that old. I knew it was more of a retro design but that is neat. Thank you for sharing.I read an article on the origini of the Kaweco Sport, 1935-1938, and that originally was a piston filler. I found one from the early 50s and bought it. it is ever so tiny compared to the modern one!!
On the left the modern one and on the right the 'original' one