Moore Pen Nibs
The Moore Company took great pride in their nibs, crafted for many years by Thomas P. Miller, "a genius in gold pen making of national reputation" [Moore Company ad]. Their early nibs are nicely flexible. The best nibs, to my taste, were the Maniflex nibs made in the late 1920s. They're generally "semi-flexible", in that they vary in line width with pressure, but basically hold an even line. Later nibs get increasingly more stiff and un-interesting, although still reasonable with which to write.
Early nib - "The Moore Pen". The earliest nibs say, "American Fountain Pen", and are found only in the early Non-Leakable pens. Some of "The Moore Pen" nibs are very flexible and are wonderful writers - comparable to the Waterman 52 in terms of flex. I value pens with "The Moore Pen" nibs as worth a premium.
The Maniflex nib - a nice compromise between the Manifold nib (meant to be stiff to go through many carbon copies) and a flexible nib. These are not consistent nibs. The more flexible among them are particularly nice. The primary Moore nib from 1929-1935.
The Moore Junior - in this case a relatively large number 4 nib in a large pen. The Junior line are lower quality in their fittings, but are often quite large. And the nibs are quite nice.
Moore 14K - heart-shaped vent hole
The Moore Maniflex Pen with a "twin peaks" design above the lettering. These aren't bad nibs, although not usually as flexible as the original, un-ornamented Maniflex.
Moore Life Maniflex nib with angled lines parallel to the end of the nib, introduced in about 1941. These nibs tend to be quite stiff and less interesting with which to write. Often found in 1940s pens with rivet caps. I refer to it as the "almost feather" model.
The famous Moore Fingertip Nib. Designed to compete with the Parker 51 and Sheaffer Triumph, it has a very modernistic appearance, unique to Moore. For whatever reason, a complete flop in sales. The writing is stiff, similar to a Parker 51.