Roy Thomas's first stint on X-Men lasted from 1966 to 1968, covering issues #20-43. He was accompanied along the way by six different artists, the foremost among them being Werner Roth, who drew issues 20-29, 31-33 and 35, and who dropped the pseudonym “Jay Gavin” after #22. The other pencillers were Jack Sparling (30), Dan Adkins (34) and Ross Andru (36-42). Don Heck took over for five issues (38-42), but relinquished the final one (43) to fill-in George Tuska. Roth also pencilled the five-issue “Origins of the X-Men” back-up storyline from #38-42.
