Parker 51

The Parker 51 is a fountain pen developed by the Parker Pen Company, an American writing instrument manufacturer founded in Janesville, Wisconsin. Development of the pen concluded in 1939 to mark the firm's fifty-first anniversary, which inspired its numerical designation and avoided translation difficulties across international markets. Formally introduced in 1941, it was marketed during the Second World War under the slogan "The World’s Most Wanted Pen", capitalizing on wartime consumer production restrictions to stimulate high demand.

The model remained in production until 1972, undergoing a succession of revisions throughout its thirty-year history, and became the most widely used fountain pen model in history. Due to wartime restrictions, Parker faced a backlog of demand that required several post-war years to satisfy. Decades later, Parker released related iterations, including the 51 Special Edition in 2002 and a reimagined version in 2021 that measured four millimetres longer than the original design. Notable users included Queen Elizabeth II, who used a burgundy Parker 51 from the 1950s onward.

The design is characterised by a hooded, tubular nib, a tubular section, and an internal multi-finned collector. These features were engineered to keep the nib wet and ensure consistent ink flow when using fast-drying ink formulations. Early production models made from 1941 utilised a Vacumatic filling mechanism operated by depressing a plunger to draw ink by vacuum. In 1948, Parker introduced the Aerometric filling system, which functioned via a pressure bar acting on a "Pli-Glass" PVC sac. The pen was designed to work with proprietary high-alkalinity "51" and "Superchrome" inks, but its construction also accepts conventional fountain pen inks such as Quink.