Seth Sears Crocker was one of the first to arrive at the idea of using pneumatic air pressure to fill a fountain pen. While Crocker pens are very collectible, it was his son, Seth Chilton Crocker who really produced the first "Big Name" pen to use this filling system, the Chilton Pen. The Chilton pens used a system similar to that later used by Sheaffer on their Touchdown fillers, a thin cylinder pulls out from the barrel. Inside this cylinder is a rubber ink sac, when the cylinder is pushed back into the barrel, the pressure generated compressed the ink sac. It's a simple, effective design, and one that allows for easy one handed use. The pens were made from 1924, beginning in hard rubber, progressing to celluloid in a few years. The range of materials used is as wide as with any of the American companies of the time, and the quality was second to none. Today, Chilton pens are considered to be very collectible, and not always the easiest of pens to find. In addition to being collectible from a standpoint of rarity, Chilton pens often make wonderful writers, with very nice flexible nibs, and great ink capacity.