I just spotted this ad in a horror comic from the 1970s, and as it turns out, the product already resides in my own collection of stuff. This would have been an easy entry in Mail-Order Mysteries, but oh, well. So here goes...
What We Imagined: The ad itself challenges us to imagine owning a set of 88 full color posters, however the next sentence clearly reveals the "miniature reproduction" detail.
What They Sent: A satisfying stack of very cool "mini posters" with adhesive backs and black light responsive ink. Offering the surplus of display decals as a stand-alone product was an ingenious idea. Kids without the funding or the wall space could still enjoy psychedelia at it's finest.
Customer Satisfaction: Day-Glowing.
(How did I get these? I ordered them years ago from a catalog called Don and Chris' Old Stuff which is now a web site. Although they only have one design left.)