The puzzle image (and the top photo in my post above) show the '1966 DOW', a scale model built by Creative Industries of Detroit Michigan. The second photo in my post above shows the '1967 DOW', which was apparently the same Creative Industries model, albeit with minor changes.
A '1968 DOW' was designed by Virgil Exner and built by Exner's employee Gene Watch (modeled in clay and finished in fiberglass). It looks nothing like the '1966' and '1967' versions, however.