Gil Kane was arguably the most important artist in the formative years of the Silver Age. Infantino's Flash came first and Kirby's Fantastic Four would be bigger when it arrived a couple of years later, but in 1959, no artist suggested the clean, muscular, graceful style of Schwartz' titles better than Kane.
Though he was already a mature artist with a fully formed style when the period started, Kane's look evolved through the Sixties. This late Sixties story from Tower's U.N.D.E.R.S.E.A Agent (don't ask) catches him late in the transition.
Kane fans should definitely check this out.