This looks to be gouache on cardboard made for art in Harper's  Bazaar magazine of June 1947. It is signed Marilyn Thayer in lower right. This does have quite a bit of spotty staining on the white edge borders as you can see in one of my closeups. The actual artwork has less staining than the edges. Definitely  needs a bit of cleaning. I'm not sure if this was a well known artist or just someone pitching her art to different companies. I have another advertising piece of hers on ebay that is for an early 1940s ballpoint pen. I've had these over 20 years.it measures 30 inches long or tall by 20 inches wide.