John Verpoorten attended New York’s School of Visual Arts, and began his career at the Tom Gill Studio for four years, working as Gill’s assistant (a position also held at different times by other Marvel alumni Joe Sinnott and Herb Trimpe). Verpoorten is known to have been heavily influenced by the work produced in the 1950s at EC Comics. In 1967, Verpoorten started working for Marvel Comics as an inker, working on a wide variety of titles. “Jumbo John” came to inking Kirby very late in the King’s 1960s Marvel era. His inking contributions were mainly on covers, including some key later Fantastic Four issues (#97 and 99), and numerous 1960s Marvel reprint books (featuring new Kirby drawings of classic scenes). But he was also beginning to be assigned interior inks over Kirby just as the artist was preparing to leave Marvel for DC in 1970, and turned in an outstanding job on two of Kirby’s final Marvel stories, in Chamber of Darkness #4 and #5 in 1970.
Verpoorten became Marvel’s production manager in 1970, in the wake of Sol Brodsky’s departure from the company to form Skywald with Israel Waldman. He was responsible for coordinating the work of writers, artists, letterers and printers, and as production manager, his hand was undoubtedly present in numerous uncredited stories, doing last-minute touch-ups and fill-ins, especially the heavy reworking on Thor #179 (Aug. 1970), Kirby’s final issue of the series. In 1975, Verpoorten also helped produce Big Apple Comix, an independent comic book published by former Marvel staffer Flo Steinberg. When Kirby returned to Marvel in the mid-1970s, Verpoorten took on the inking responsibilities on the first four issues of Kirby’s Eternals series, and on two of his Captain America Annuals (#3 and 4) and one issue of the regular Cap series. In addition to working on other titles and artists as an inker, he maintained his position as Marvel’s production manager for seven years, until his death in 1977. [source: en.wikipedia.org]