Here's a little more on Gil Kane's mysterious, lost strip Jason Drum, thanks to Bronze Blog Buddies George & Joe. From George, this is the one other available piece of art from the strip, a cover from 1979:
General consensus is that it ran in Tintin magazine, and was written by Michel Greg. Gil only did the first 15 pages, (assisted by Joe Staton) and the suspicion is that they might've been leftover pages from the aborted third Blackmark book, that Greg then rejigged into a new series. According to Joe, an artist named Franz Drappier then took over the piece, although the serial was never completed. And that's unfortunately all we know. Weird that there's just no info on this strip, and Gil's pages have never been reprinted anywhere, 'cos I'd sure like to see 'em, for one.