The band went through further personnel changes until 1969, when they were given a professional performance license, which was all-important in East Germany. By then, Jacob had been replaced by Gunter Wosylus and vocalist-guitarist Dieter Birr had joined, cementing the band's lineup for the next ten years; the band dates this, rather than 1965, as its foundation. (The two Dieters are differentiated by their nicknames: "Quaster" Hertrampf, from a corruption of the title of The Shadows' "Quartermaster's Stores," after his long attempt to learn the Hank Marvin guitar solo; and "Maschine" Birr, once called an "eating machine" by his bandmates for his voracious appetite).