The company first acquired the patents for the Pelikan fountain pen (using solid ink) from the Croatian chemist Slavoljub Eduard Penkala, and in 1925 acquired the patent of Hungarian engineer Theodor Kovacs for modern fountain pens with a differential piston system. In 1929 Pelikan started producing fountain pens with its piston filler, later known as the Model 100, the first Pelikan fountain pen. The piston mechanism provided a smoother flow of ink without blobbing or leaking, in addition to a larger supply of ink. The peculiarity of this pen was the differential screw system. The green marbled binding and the semi-transparent ink window were the visible trade mark of this pen. In the upper price segment, Pelikan brought out the first Toledo fountain pen in 1931.
By 1938 and the 100th anniversary of the company, Pelikan employed 3,700 people. By the outbreak of the Second World War, the company employed nearly 5,000 people with factories in many European countries and in South America (Brazil). The Second World War with the general scarcity of goods forced Pelikan to restrict its product offering and to use substitutes for some materials. Due to the of labor initially shortage more women were employed, but also POWs and forced laborers. As a consequence of the war the company lost their foreign based factories through expropriation.
In the years after the Second World War Pelikan experienced an economic boom and became a leader in the industry. This was due mainly to the 1950s introduction of the Pelikan 400 fountain pen, which became known as Stresemann. This pen had a barrel with green / transparent stripes. The designation goes back to the striped trousers of the Stresemann-style suit, which is named after the German Foreign Minister Gustav Stresemann. Fountain pens were henceforth one of the most popular products of Pelikan AG. In addition to the green / transparent version,a brown / black / transparent version also existed, which can still be quite frequently found on pen collectors' forums. This pen was modified again and again from the 1950s onwards and is still available in only slightly modified form. In the 1980s Pelikan expanded this series to the M600 and M800 fountain pen and brought all these models together in the so-called Sovereign (Souveraen) series, the purpose of which is to provide customers with the best writing experience possible. The cheapest priced among Pelikan's modern pens is the series of M150 to M250, which mainly differs from the Sovereign-series, in that it is equipped with a stainless steel nib. Writing instruments in the Sovereign series have two-tone gold nibs in 14 (585) or 18 carat (750). Pelikan is one of only a few manufacturers who produce the nibs of their fountain pens for themselves instead of buying them from a specialised nib manufacturer. In the 1990s, the Sovereign series was complemented by the largest model M 1000, and it was also at this time that Pelikan started to produce limited editions.
In 1960, the Pelikano student fountain pen was introduced to the market. In the early 1970s a simplified script was developed by educators with the help of Pelikan, and was partially incorporated in school curricula.