In the early days of this blog, I noted that Mike Zeck didn't do much X-Men art. Will's Comic Art Page proved me wrong, with this promotional image of the Beast. According to the site:
"The Beast was a piece of presentation art done for a sales presentation at Marvel Comics. Mike Zeck pencils, Joe Sinnott inks and it was colored later by Tom Smith. There are other pinups that were done for this presentation such as the Toad, the Blob and other X-Men characters as well."
If anyone knows about the other pinups, please feel free to contact me!