Well, all sources I have available tell me this is the May 1985 issue of Polyhedron, however the cover and content are clearly April Fool’s themed. So, it’s probably the case that this issue would have been sent during the month of March/April to subscribers (this wasn’t really being sold widely in stands, being mainly a subscription perk for RPGA members). If you aren’t familiar with the magazine publishing business this is usually the way it is: the date on the cover means when you take the issue down from sale rather than when it’s put on sale. 

But hey, this gives us a ton of fun stuff in the quite short magazine (some 30 pages). To star off we have a great cover by the always amusing Tom Wham, a game designer and illustrator which has an unmistakably whimsical style, and there are references to the articles inside the magazine on the cover, which is pretty fun. There are humorous articles inside about Gargoyles, funny campaign encounters, songs for your party to sing while dungeoneering and even a silly class by Gary Gygax: The Ultimist.

There’s also serious content here, mainly represented by the second part of the adventure module “In the Black Hours” that had started out in the previous issue and fortunately didn’t take a turn for the humorously zany in this one.