Just finished repairing a ca. 1920 fountain pen, the Conklin Crescent Filler, given to me by a friend, and now one of the oldest fountain pens in my collection. This is a photo of one fully restored -- mine looks just like it but still needs a new clip. This 90-year-old pen writes better than any modern roller ball or gel pen, putting down a perfectly smooth, wet line. The body is made of black chased hard rubber (BCHR), and the nib is a gold no. 2, made in Toledo.
This is the model pen that Mark Twain used. He acted as a spokesman for the Conklin company. In one advertisement Twain said, "I prefer it to ten other fountain pens, because it carries its filler in its own stomach, and I can not mislay even by art or intention. Also, I prefer it because it is a profanity saver; it cannot roll off the desk."
Richard Binder's page on the Crescent Filler is here. Interestingly -- well, maybe I'm one of the few who find it interesting -- the Conklin Crescent is being remanufactured by a new Conklin company. Here is the new version: