A little more info...the overall poster looks screen printed or possibly hand drawn and the giantess image seems to be appended on top of the main poster. However the faded 1958 stamp touches both 'individual' parts so it is not like the image was added later (after the fact).
The person I got it from was a set designer for many years and collected many movie pieces from the US and Toronto. He had this piece for many years as I believe he found it in the 1970s. When I saw it in his collection, I knew I had to have it. When he saw how taken I was with it, he gave it to me as partial payment for a film I acted in.