 It was produced at a toy factory in Roudnice nad Labem.It was not until 1940 that it achieved its remarkable level of popularity, when Jaroslav Foglar published "Záhada hlavolamu" (Mystery of the Conundrum), the first part of his sequence of stories about the Rychlé šípy ("Rapid Arrows") boys' club.Rychlé šípy comics series began to appear in the magazine "Mladý hlasatel" (Young Herald) in December 1938, and gradually became the most popular series in the history of the Czech comics.