An excellent site, Visco, has lots of pulp sf, adventure and mystery magazine covers. Phantom magazine is a new title on me, but it's interesting to note that somebody once tried to produce a British equivalent to Weird Tales, and even used some WT content.
It ran for 16 issues in 1957-8 and was published successively by Vernon Publcations, Dalrow publications and Pennine Publications though, as these were all based in Bolton, Lancs, it is likely that they were connected. It had as sister publications the Creasey Mystery Magazine (later, under different ownership, John Creasey Mystery Magazine) and Combat, bizarrely advertised inside the cover of one issue of Phantom as the GOOD War Story Magazine. It isn't clear whether the wars were good, or the stories.