It's a new parlor game! One blogger guesses Stan Lee although he was going by memory rather than rereading my original post. I don't think he's right as the art probably sat around for years after it was first published, and as one of his commenters also noted, Sara Duke says it was given to the donor as a gift that he's now passing on. Blake Bell for example has demonstrated that the artwork was reshot again years later for reprints in Marvel Tales, for instance. Also it wouldn't have to be one of the original bullpen members as it wouldn't have been considered that important until the Marvel offices had grown a lot.
Wow, Sara Duke is the new version of Woodward and Bernstein. Who is DEEP POCKETS?