Frankly I would just as soon have taken advantage of the easy interchangeability of Pelikan nib units to put that old flex nib onto a modern Pelikan barrel, if the vintage barrel weren’t a beautiful tortoise-shell stripe celluloid. So I got it fixed. (I once briefly had a modern tortoise-shell stripe M400, very similar to this vintage 400, but sent it back because the nib was defective.)
I have one other vintage pen but it’s a no-brand thing that got lost, with its mates, in the back room of Woolworth’s or whatever and was forgotten for 50 or 60 years. Made in Germany shortly after the War (probably not by Pelikan), and a total piece of crap. Not my best purchase ever.