Here we see three looks at this classic T.H.U.N.D.E.R. image. First, the original art, above, which Dan Adkins noted in COMOC BOOK ARTIST that he had done everything but ink the Dynamo figure.
Then, the published version above from the first issue of DYNAMO in '66. Then finally, below, an all-Adkins version in the form of a re-creation down, I believe, sometime in the 1990's.