Fischertechnik has produced myriad different sets over the years, and the company has several times renamed existing sets. Moreover, there have been as many as five different lines of these sets (often referred to as "A", "B", "C", "D", and "E" in fan circles) with similar but differing components (all compatible, of course). Roughly these fit into the production years 1967–1971, 1972–1975, 1976–1981, 1981–1984 and 1984–1991. The A line featured predominantly black-and-white images, whereas the "B" line features the "Oscar DuJouet 1970" award on the box design. "C" saw the introduction of black plastic cogs (earlier they were all red), and "D" saw the introduction of yellow plastic "statics" (whereas before they were grey).