No, of course WT didn't hype 1975...the rank and file came up with the concept all on their own and even managed to get their ideas into WT literature and preach it for several years before WT caught on. Sneaky devils, those R&F.
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Awake! 1969 May 22 p.15
"If you are a young person, you also need to face the fact that you will never grow old in this present system of things. Why not? Because all the evidence in fulfillment of Bible prophecy indicates that this corrupt system is due to end in a few years. ... Therefore, as a young person, you will never fulfill any career that this system offers. If you are in high school and thinking about a college education, it means at least four, perhaps even six or eight more years to graduate into a specialized career. But where will this system of things be by that time? It will be well on the way toward its finish, if not actually gone!"
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1968: "Why Are You Looking Forward To 1975?" … "What about all this talk concerning the year 1975? Lively discussions, some based on speculation, have burst into flame during recent months among serious students of the Bible. Their interest has been kindled by the belief that 1975 will mark the end of 6,000 years of human history since Adam's creation. The nearness of such an important date indeed fires the imagination and presents unlimited possibilities for discussion." (Watchtower, Aug. 15, 1968, p. 494)
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1974: "Yes, the end of this system is so very near! Is that not reason to increase our activity?...Reports are heard of brothers selling their homes and property and planning to finish out the rest of their days in this old system in the pioneer service. Certainly this is a fine way to spend the short time remaining before the wicked world's end." (Kingdom Ministry, May 1974, p. 3)
Of course, WT has gone down this road before...and failed then as well. Compare to this statement to one made 58 years earlier:
1916: "We see no reason for doubting, therefore, that the Times of the Gentiles ended in October, 1914; and that a few more years will witness their utter collapse and the full establishment of God's kingdom in the hands of Messiah." (Watchtower Reprints, VI, Sept 1, 1916, p. 5950)