The contest mentioned on the cover is on pages 47-50 (interrupting Sequence 2). The contest closed on 30 June 1980.
This cover is based on the first page of the story "Climax" in Adventure Comics (DC, 1938 series) #463 (May-June 1979)
These three orginal stories have been merged into a single story. The titles and credits have been removed from the start of "Executive Action", with the entire splash page removed from "Climax".
Origin and first appearance of the Sea Devils.
This contest is sponsored by long-running Murray advertiser, Seven Seas Stamps, and features the "Murray the Cat" mascot.
It isn't clear what this advertisement is promoting as Murray didn't have a regular Flash series at this time. The last issue of The Flash Album (K. G. Murray, 1976 series) was late 1979. Flash stories did appear in some issues of Super Action Album (K. G. Murray, 1980 series) and Super Heroes Album (K. G. Murray, 1976 series) at this time.