It was clear, it's from the mid 60s since 'Crucifix' was out already but they still hope for 'Outsider #4', which we know now, never appeared. (and they even name 1964 to be past and 1966 to be at least not over.)
From the measurements looking square, I had thought it was on or inside an LP-cover, but you said it's a big paper. I ain't sure if you'd consider 'WR' big. I wouldn't, for it was important but not really "big", right? But then I must admit: I know of No really big paper back then to print Buk "several times".
I'd say, mjp, tell us the story. It isn't cheating: Every thing one of us knows, is only b/c we've read it somewhere or been told. What else would be our sources? (except first-hand experience, but that covers less than 2% of all trivia-questions here, right?)