When I handed in the inked cover (as you see it here) the editor said "How will we know it is Sherlock Holmes" I agree with the comment posted above: don't need the hat. Still and all, the Editor said: draw the Deer Stalker and we'll paste it onto the art.
I said "grrrrrrr", to myself, and sent a half-page on which I'd drawn 6 "hats"... a Straw Boater, a "Newsboy", probably a Top Hat, the Deerstalker and, forgetting the final hat (which MIGHT have been a Shadow Hat), I did draw a Sony Walkman set of Earphones. I put a pencilled indication of where Holmes' ear should be so whatever "hat" they'd choose, it'd rest on his head accurately... well, to my eye, they muffed that: it looks like The Batman just sort of bumped the back of the Deer Stalker and pushed it forward, in an almost comical position...
Grrrrrr, again!