How were vintage pens made?
Modern pen manufacture is highly automated and very much oriented towards mass production. Prior to the '40s, however, pen making was labor intensive and involved a great deal of hand fitting. Whereas most postwar pens have used injection molded plastics (including Montblanc's so-called "precious resin"), earlier materials such as hard rubber, casein, and celluloid had to be machined to shape.
One of the most skilled tasks was the making of nibs. Modern nibs tend to be made in a rather limited variety of tip widths, and few have much flex. While some are somewhat "soft", this yielding quality is quite different from the springy action that pen fanciers so prize in vintage nibs. Making gold nibs that are both resilient and not too hard is not easy even now, as springiness is obtained only by careful work-hardening of the material -- a process more art than science.
Clips and other metal fittings were stamped, then and now, though nearly all modern pens use thin electroplate instead of heavy gold filled parts. Smaller firms often obtained metal parts from subcontractors, including nibs. Bands and overlays were rolled from sheet and hard soldered; for the most part they seem not to have been cut from extruded tube stock, which was not available in the requisite thinness.