Some information on this issue supplied by Tom Lammers and the Atlas/Timely discussion list.
in Sinister Tales (Alan Class, 1964 series) #69 (1969)
in Secrets of the Unknown (Alan Class, 1962 series) #156 (none listed) [original title: I Died Tomorrow!]
in Secrets of the Unknown (Alan Class, 1962 series) #156 (none listed) [original title: The Brute!]
in Sinister Tales (Alan Class, 1964 series) #69 (1969)
in Secrets of the Unknown (Alan Class, 1962 series) #156 (none listed) [original title: They Crawl By Night!]
in Secrets of the Unknown (Alan Class, 1962 series) #156 (none listed) [original title: What Stanley Saw!]
from Mystic (Marvel, 1951 series) #40 (October 1955) [as "The Thirtieth Century"]
in Sinister Tales (Alan Class, 1964 series) #209This story is set at the end of the 29th century.
in Sinister Tales (Alan Class, 1964 series) #69 (1969)
in Secrets of the Unknown (Alan Class, 1962 series) #156 (none listed) [original title: The Man Who Crushed Rocks!]