He's back! Krypto seems meant to have been a one-shot like so many other super-stories but they must have gotten mail. Hard to tell since letters pages had yet to be introduced. EC had them. So did Lev Gleason comics since the forties. I think even Timely had them for a period. Seems like they would have been cheaper than paying a writer to churn out text stories that almost nobody read month after month after month just to comply with second class postage regulations.