Continuing to pile on Krypton coincidences, Superman #103 (Dec 1955) establishes that Superman’s grandfather had visited Earth 60+ years prior using an “experimental space machine”. Boy, that machine must have had serious problems that led to technological upheaval because Jor-El only manages to build a prototype space rocket to save his son thirty years later… 😛
Superman’s grandfather was at various times named Jor-El the First (pre-Crisis) or Seyg-El (post-Crisis). Outside of canon, Superman’s grandfather, Seg-El, became the focus of the SyFy TV series Krypton.