Aside from these sporadic works, however, Sinnott was primarily inking for Charlton during this period, with occasional jobs for American Comics Group, "Treasure Chest", and Dell Comics, for which he variously penciled and fully drew film and TV adaptations, and penciled the one-shot biographical comic "The Beatles" #1 (Nov. 1964). But then, in 1965, he returned to Marvel to work virtually exclusively, beginning with his inking the cover and the story, "Where Walks the Juggernaut", of "The X-Men" #13 (Sept. 1965).