Conway Stewart nibs
Conway Stewart probably didn't make nibs before 1920, and all the earlier pens are fitted with "Warranted" nibs. Later they fitted thier own nibs with the typical Conway Stewart logo.
Its difficult to show photos of nibs because of the distortion at the edges when taking macros. So, instead I have drawn them. Each pen number has its own nib size, the largest one being a number 6. Basic differences between nibs are: angled logo (early) or horizontal logo (later); nibs with circular breather holes and nibs with heart shaped holes; nibs with the "C" enclosing the "o" of the logo, and nibs with the "o" outside; the position of the curved tail of the "y" etc; and of course the Duro nibs (thicker) and the Manifold nibs (even thicker).
It seems a bit crazy to research the nibs, but sometimes its nice to know if your favorite pen is fitted with the correct nib.

Conway Stewart Nibs

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These pictures are admittedly not good (they were taken using a scanner) but they show the problem of taking close-ups of convex objects.