Mid-century vintage 1940s pulp science fiction magazine, "Astounding Science Fiction" from September, 1949. The cover story for this issue is "The Double-Dyed Villains", by Poul Anderson. There are also stories by L. Ron Hubbard, Isaac Asimov and others.
This is in nice vintage condition. We don't know anything about grading pulp magazines, but this issue does have some wear and age. There is some staining to the back cover and there is also a "79" in ink on the bottom edge of the pages.