In Flash #129 (April 1962), Barry Allen gets his second crossover with the Golden Age Flash, Jay Garrick. We start on Earth-2 (just called “Another Earth” in this issue) with Jay Garrick reminiscing with his wife Joan about his adventures with the Justice Society years ago. There’s a couple nice pages where the Golden Age Green Lantern, Hawkman, Atom, Dr. Mid-Nite, Black Canary, and Wonder Woman are all battling The Key.
The Golden Age Flash discovers a meteor is necessary to preventing a planet-wide radiation catastrophe, but the meteor has gone missing. Jay decides to cross over to visit Barry’s Earth to see if the meteor exists in that universe.
Meanwhile, Captain Cold and The Trickster team up on some crimes and end up doing battle with the Flashes of Two Worlds.
The criminals are apprehended, Jay excavates the meteor into ingots and synthesizes enough for both Earths. The story is kind of meh, but it’s still pretty cool to see Gardner Fox experiment and lay the groundwork for a full-blown multiverse, reviving characters from twenty+ years ago. For example, it’s the first time that it is established that the Wonder Woman from the 1940s is a different character from the Wonder Woman of the early 1960s, though she’s actually been in continuous print the entire time. The Superman and Batman of the JSA are not yet mentioned. Anyway, I’m very happy that the JSA revival has begun!