From DC Special Blue Ribbon Digest #3. Apologies for the poor quality. My digest is pretty worn and I don't think it would've survived being flattened on the scanner.
Makes you wonder...
If they had named the Earths in reverse, with Earth-1 being the Golden Age JSA and Earth-2 being the Silver Age JLA... they could have had an Earth-3 that spawned out of Crisis featuring a new generation. It would continue the concept of each new Earth having heroes first appear 25 years after the prior one.
Hmmm... and technically the New52 would fit as Earth-4.