I also remember stories like that floating around about 1975.
One variation had it that, when a ouja board was asked about the prospects for the year 1975, the thing promptly disintegrated. Talk about wild and sensational rumours!
Having been an avid reader of all Watch Tower Society publications from 1966 until 1994, I know what they said.
They are to blame for the 1975 fiasco, however much they have tried to deny it ever since. Just one example out of ever so many was the Awake article in October 1968. I forget whether it was October 8 or October 22, but I certainly remember the article well : - "Are You Loooking Ahead to 1975?". It made the point that if any faithful "Christian' wasn't looking ahead to 1975, then it was high time that they were!