ICN made posters of current events that would be hung in public places, like bars and taverns. They were quad-folded for mailing and are about 16 x 20 (not sure of exact size but big enough to be annoying to store) There were other manufacturers as well in the same business. Here is an example from a competitor with a similar size and stock as yours:
Also blank-backed. I suspect that these were made for bars and taverns that did not want to take up the space for a poster.
My experience chasing Louis premiums is that the posters can be found but the smaller card stock pieces are rare. I'd guess yours falls into that category.