Martin Key is listed as the illustrator in the debut issue of If magazine, March 1952. The cover illustration is this:
Wikipedia has nothing. Amazon has nothing (not surprising, maybe 1 in 20 of the classic pulp illustrators will have an art book). I have no proof the man ever existed, it was perhaps a pen name.
I have went through almost all issues of this magazine title, and it seems he had never done another cover for it. Though, in that era, there were three or four dozen science fiction magazines, and a thriving paperback novel market.
I would like any details about this artist that may be available, even just other titles that he provided artwork/illustrations for.