The initials are familiar to me, maybe because I have the same poster...
I did look into it a couple of years back, when searching for a couple of U.K. poster artists; and the closest I came was Eddie McKnight Kauffer (E.Mc) But it's so not his style, and he died the same year of the film 1954. Again very unlikely to be him. I remember searching for the couple of names I had, was very annoying as I kept drawing blanks, so was trying to look up Alias's, and all kinds of permutations of the names.... in fact the only one I found was Jon Kaye an artist for R.K.O. Which just goes to show, the Inter-web is not as good as it's cracked up to be...
So can't help either,