I promised Jack Cole, and here he is with the very busy cover to Silver Streak Comics #5 from July, 1940 making this the front runner for the earliest Sneak a Peek Cover. There is so much going on here that you almost don't notice the Sneak a Peek aspect. It's nicely done, with Dickie Dean teasing the kids, promising plans to some fantastical invention (I wonder what it was). No interior narrative here, but at least a hint of panels. Both Ace Powers and Lance Hale (love those names!) seem to have their hands full. Perhaps Dickie could invent something to help them.
Next up is a personal favourite of mine, the cover to Frisky Fables Vol 1 #1 (Spring, 1945). As far as quirky funny animal covers go, I'd put Al Fago right up there with LB Cole. OK, maybe not right there, but he gets the silver medal. I really like they when this one is constructed, right down to the rather elastic nature of the corner being pulled. We get just a hint of the inside narrative. If the indica had been included it would have been perfect. This series has so many great 'theme covers' including an including two infinity covers published in the same year. I've got them both.
Finally, we come to Jack Burnley 's wonderful cover to Batman #42 (Aug-Sept, 1947. Burnley really was a master at cover design, and his Sneak a Peek cover here is perfect for Catwoman's second cover appearance. I think that one of the reasons Catwoman became so popular (aside from the awesome costume) is that so many of her cover appearances are truly iconic. This one is great, as Selina is trying to hide out inside the pages of the books. It's very clever and one that I've been trying to track down at a reasonable price for a long, long time.