Posted By:
barrysloateThere must have been a lot of posters circulating, and virtually all of them were cut down. You can also find N28's and N29's with blank backs, likewise cut from advertising banners.
I think the only reason these cards survived at all is that they were cut down to size. The posters easily damaged and at some point would have been "discarded" (good word, don't you think?).