Challengers of the Unknown (vol 1) #80 FN

According to splash page:  Reprints Showcase #11 (Nov-Dec, 1957)

Contains:

The Day the Earth Blew Up, Pt. 1. (pg. 1)

The Tyrans, Pt. 2 (pg.9)

The Thing that Came Out of the Sea, Pt. 3 (pg.18)

One Minute to Doom, Pt. 4 (pg. 25)