There was a definite style change from Early 70's Morison to Late 70's Morison. Early Morison was good, but simple. Illustrations were clean and dynamic, but color palettes and figure detail wasn't as cohesive as it could be. I think he was just getting a feel for the medium and what worked vs what didn't. I'd call his early backglasses more akin to comic "panels" - gets the job done, but nothing crazy.
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When he started mimicking Jack Kirby though (honestly, who didn't back then?), his stuff just rocketed out of control. Color choice, composition, line work - all amazing stuff. These I would call comic "covers," and represent some of my personal favorite pinball era for art. Even beating out most of the early 80s stuff, which was also amazing.
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