The cover of The Three Faces of Time, which I bought yesterday at a used book store in Moose Jaw, Saskatchewan, is uncredited, and no signature is visible, but it sure looks like the work of Jeffrey Jones, circa 1968-69, to me.
UPDATE (24 July 2010):
This just in: reader Patrick Hill points out in the comments section of this post that Jones informed him ten years ago that he (Jones) swiped the pose of the main figure in Seetee Shock and The Three Faces of Time from “H2O World,” with story by Larry Ivie and art by Al Williamson and Roy Krenkel. Here’s the ocular proof:
If nothing else, the above news should make Maroto fans smile.