Anna

Quite true.
And more than ever I'm convinced this is apparently a US thing. I just can't recall hearing anything particularly emphatic on this matter, other than magazine statements here and there with qualifiers as quoted above, and US CO talks on cassette tapes with starry-eyed brothers saying "You've got to listen to this!".  And of course the odd brother who were (at our level) viewed endearingly as "eccentrics".
I remember meeting an old friend on the street in early '72 who told me, cynically, that I was expecting the world to end in 1975. I didn't know much about that idea then, but I just said to him well, if it doesn't, we will both be here, but if it does, who will be laughing then? I didn't even bother to follow it up after at all. In reality, it just didn't figure in my day to day thinking. But it certainly effected some it appears.
It was most definitely NOT a big subject in my experience on a KHall level, neither in the book studies (apart from a brief flurry in the Nations Shall Know study). It didn't figure at at all in my Bible Study coming into the truth. (I was asked to study the Life Everlasting book, but I rejected it over some sort of "great tribulation" confusion.) I remember a  group of witnesses from my area moved to California in '72. They were very "end soon" oriented I remember, but we just thought they were "over the top"!
It must be a "British" thing. As far as my limited experience goes, we were just not swayed by American hysteria on this matter. We took no notice of end date statements. Maybe we were ALL APOSTATE!!! 

w86 3.15  "Yes, Jehovah’s people have had to revise expectations from time to time. Because of our eagerness, we have hoped for the new system earlier than Jehovah’s timetable has called for it. But we display our faith in God’s Word and its sure promises by declaring its message to others. Moreover, the need to revise our understanding somewhat does not make us false prophets or change the fact that we are living in “the last days,” soon to experience the “great tribulation” that will pave the way for the earthly Paradise. How foolish to take the view that expectations needing some adjustment should call into question the whole body of truth! The evidence is clear that Jehovah has used and is continuing to use his one organization, with “the faithful and discreet slave” taking the lead. Hence, we feel like Peter, who said: “Lord, whom shall we go away to? You have sayings of everlasting life".
The problem as I see it is in the FDS/GB's reluctance to make a definite distinction between when they mean themselves and when they mean everyone else. So it's  us/we/some/our/Jehovah's people etc.... all in the one basket. And yet, as we know, when it comes to making decisions on what to believe, everyone else has absolutely nothing to do with it, so any obscuring in that regard is just silly really. It does confuse the issue temporarily, but not for long and it just causes annoyance and becomes counter productive. It's very short sighted and I wish they would stop it.
It's what in England we call the royal WE, it isn't we, it's just ME!
 

Do you have any concrete evidence for that?

I was being sarcastic

I was hoping that the reason why 1975 was brought up again (at convention) was because it was a reminder that the Slave err, and that some of the new things i.e. the OVERLAPPING GENERATION theory was perhaps to be treated with caution.
But how wrong I was!....... listening to Br.Herd.... we have finally got THAT part figured out!

About Charles Sinutko, the District overseer who was one of those who publically, in  front of a very wide audience made several very pointed remarks about 1975 including those already stated on this thread such as ““they know what’s coming, and don’t wait till 75, the door is going to be shut before then!”. No doubt he was one of the contributor to the 1975 “frenzy”.
However, Reading his life story in the  2004/8/22 Awake  it is evident that he is one of the ones “who made the needed adjustments” and who “didn’t run away and didn’t give up” (as per the video) Did he suffer selective amnesia? Surely not...   We don’t know what he thought, because he doesn’t say, but I can picture there must have been some interesting discussions between him and others after 75.
The question has been raised on here, what was the purpose of bringing up 1975 again at the last (2017) convention, and then some theories as to why.
The video was part of the talk “How you can by no means ever fail" based on 2 Peter 1:5-10; Isaiah 40:31; 2 Corinthians 4:7-9, 16
I don’t have time to figure out how to isolate the video from the rest of the talk to post it on here,  but here is a “transcript” beginning with Rachel’s father talking to his grandson with whom he had just attended pioneer school:
“Hard to believe this system would last so long, and I certainly would never believe I would be a grandfather”. Then he goes on to relate how his wife died and how “with Jehovah’s help and the support of the brothers we got through it”.
We learned to rely on Jehovah in ways we never had before – and that helped us when years later, another test came our way. You see, back then, some were looking to a certain date (1975) as signifying the end of this system of things and a few even went as far as selling their homes and quitting their job. I admit, I was ready to see this old system go away too. But something just didn’t seem right. Both at meetings and personal study – I was reminded of what Jesus said “nobody knows the day or hour” . I was dedicated to Jehovah, not a date. After that year came and went most of those who had wrong expectations made the needed adjustments…..and they stayed. We didn’t run away and we didn’t give up. We trusted in Jehovah. And when I see older ones now, I don’t just see grey hair, I see living breathing examples of endurance”.
So what IS the lesson?

Just steering a little back to 1975, I think maybe the confusion and conflict in this thread regarding what "really" happened apparently come from the fact that some of us are talking about stage 2 and 3, and others about stage 4 and 5. So two different aspects of what was said about 1975, and both aspects are true.
The 5 stages as posted by JWI, as a refresher:
1.The initial idea is floated, often with a bit of caution.
2.Then someone is sure enough to begin championing the prediction and begins to stake their reputation on it.
3.Then as confidence builds, those statements become more and more direct and less careful.
4.Then as the time approaches and the kinds of surrounding expectations that might have validated the prediction aren't there yet, real caution kicks in, and if necessary, some backtracking begins.
5. After the failure is obvious, we can expect blame and finger-pointing.
 

Do you have any concrete evidence for that?

Yes, as I thought the whole thing was ridiculous, and drew many satirical cartoons on the inside covers of theocratic books, reacting to what the speakers from the platforms were saying, as they expounded with MANY words  .... making fun of the whole idea ..... from about 1970 to 1974 ... ( I may still have them here somewhere in a box ... I am like a pack-rat ...) but after being bombasted  by  "1975-1975-1975 !" at every angle for three years, I concluded that it was VERY IMPROBABLE ....  that every  JW I knew, from Virginia to California would know something as a fact that I was not aware of .... so, in late 1974, I "caved in", and quit my job in Zaire, the Congo, and flew back home to Virginia to be with my parents when the "end came". 
It still made no sense to me ... I suppose I had faith in the Brotherhood from top to bottom to have more "faith" than I had, and SUPPOSED my mind was clouded ... as I am basically a Barbarian in nature.
If my parents were going to die, I wanted to be at home in Virginia to die with them ... because I STILL did not believe it.
It was a kind of "just-in-case" thing.

Let's baptize pregnant mothers.........

I think this series of stages, while not definitive of course, helps put a framework on statements made during this time period and others too. For example, before 1925 the statements were very definitive about the "end" in 1925, and all caution was thrown to the wind in 1924. The statements became more cautious in 1925. There was another stage somewhere between 4 and 5 in those days where the Watchtower just denied that they ever said the things they said. Naturally, those who wish to defend the Watchtower Society against having made a false prophecy about 1925 will quote the stage#4 and stage#4.5 statements, and those who wish to embarrass the WTS will quote the stage#2 and stage#3 comments.
As to the "finger-pointing" stage#5 note the similarity between the following two statements, especially the portion highlighted in red:
*** yb75 p. 146 Part 2—United States of America ***
God's people had to adjust their thinking about 1925. . . . . A. D. Schroeder states: “It was thought that then the remnant of Christ’s anointed followers would go to heaven to be part of the Kingdom and that the faithful men of old, such as Abraham, David and others, would be resurrected as princes to take over the government of the earth as part of God’s kingdom.” The year 1925 came and went. Jesus’ anointed followers were still on earth as a class. The faithful men of old times—Abraham, David and others—had not been resurrected to become princes in the earth. (Ps. 45:16) So, as Anna MacDonald recalls: “1925 was a sad year for many brothers. Some of them were stumbled; their hopes were dashed. They had hoped to see some of the ‘ancient worthies’ [men of old like Abraham] resurrected. Instead of its being considered a ‘probability,’ they read into it that it was a ‘certainty,’ and some prepared for their own loved ones with expectancy of their resurrection. *** w76 7/15 p. 441 par. 15 A Solid Basis for Confidence ***
If anyone has been disappointed through not following this line of thought, he should now concentrate on adjusting his viewpoint, seeing that it was not the word of God that failed or deceived him and brought disappointment, but that his own understanding was based on wrong premises. *** w80 3/15 p. 17 par. 5 Choosing the Best Way of Life ***
. With the appearance of the book Life Everlasting—in Freedom of the Sons of God, and its comments as to how appropriate it would be for the millennial reign of Christ to parallel the seventh millennium of man’s existence, considerable expectation was aroused regarding the year 1975. There were statements made then, and thereafter, stressing that this was only a possibility. Unfortunately, however, along with such cautionary information, there were other statements published that implied that such realization of hopes by that year was more of a probability than a mere possibility. It is to be regretted that these latter statements apparently overshadowed the cautionary ones and contributed to a buildup of the expectation already initiated.

Just so you know @DespicableME, I removed my own comment regarding a link about a porn star who left the JWs. With that comment gone, your comment in response to it (referencing Ruud) seemed even more out of place, so I deleted it along with mine. I didn't do this as a censorship, just didn't want to make your comment seem more awkward than it was.
Just so you know @Srecko Sostar someone (not me) moved your comments about copyright to a new topic, linked below, so I moved the other followup comments from this topic over there too, which included a couple of my responses. I ended up dragging over about 10 comments that had veered off onto that topic, also affecting comments by @DespicableME and @Noble Berean
 

It would accomplish two irresistible aims of certain religionists. (Thank God they are not us)
It would validate those Middle Ages portrayals of the Savior with golden flowing hair.
It would affirm the U.S.A. as God's chosen vehicle.

No.......but I can discuss this in the appropriate topic

I thought it would be a good idea to look into the ways in which we defend ourselves against the claims about 1975, and the way in which we answer questions about it. As a good example I will start with the way in which a person answered a 1975 challenge on YAHOO ANSWERS. The person signed their name as BAR-ANERGES. I'll assume the person is male. He is evidently not a member of this forum, and may no longer be alive, for all I know. But if anyone knows him, or his whereabouts, I hope he gets a chance to respond himself.
I'll just make some short comments to state my own opinion of what he said. I'll mark his words in a different color, like red.
It is an absolute lie to claim that the Witnesses said that Armageddon would come in 1975. He's right that it is incorrect to claim that "the Witnesses said that Armageddon would come in 1975." For a couple of reasons.
The most important reason is that this supposed claim is a kind of "straw man" that is worded in such a way that it diverts attention from the main point. It's true that no Witnesses should have been saying that Armageddon would come in 1975, in the sense that it must definitely come in 1975. The real question should be whether the claim is true that Jehovah's Witnesses promoted the idea that the Bible had marked the year 1975 in such a way that we could confidently claim that Armageddon should be expected within just a few years, or even just a few months, from the year 1975. Did Jehovah's Witnesses make use of this particular time period that focused on the year 1975 to justify the claim that people should decide quickly to convert and join the organization of Jehovah's Witnesses for safety from imminent destruction at Armageddon? Also, the term "the Witnesses" can refer to a wide range of people and opinions. If we accept that the views of the Witnesses are represented in Watchtower publications, then we also have to accept that not everything said about 1975 was completely consistent. If we accept that the views of the Witnesses are represented by the Watchtower's traveling representatives (circuit overseers, district overseers, branch representatives, Watch Tower Society directors, Governing Body, etc.) then again we have to accept that not everything said about 1975 was completely consistent. Anna has already pointed out that Charles Sinutko's infamous talk is not even consistent within itself.  Here is an article from *1974* that I carry around with me which shows what mature Witnesses knew and were saying: This statement should raise a red flag immediately. We already know that not everything that was said or written was consistent. So we should be immediately wary of making use of one specific statement to generalize what "mature Witnesses knew and were saying." Also, if we look carefully at all the statements in the Watchtower publications from 1966 to 1975 we can see that by October 1974 the trend of the statements about 1975 had already begun to be more cautious. The most direct statements were made from 1968 to 1973. This is a typical pattern with predictions. It happens in corporations, political and economic analysis, and religion:
The initial idea is floated, often with a bit of caution. Then someone is sure enough to begin championing the prediction and begins to stake their reputation on it. Then as confidence builds, those statements become more and more direct and less careful. Then as the time approaches and the kinds of surrounding expectations that might have validated the prediction aren't there yet, real caution kicks in, and if necessary, some backtracking begins. After the failure is obvious, we can expect blame and finger-pointing. Statements about the time period dating back to 1956 were in stage #1. Statements in 1966 were already in stage #2. Dozens of district overseers and circuit overseers along with statements by the service department until 1973 were in stage #3. F.W.Franz himself appeared to remain in stage #3 until 1975, but he also had vacillated into stage #4 at times during the 1974-1975 period. The 1974 summer assemblies, and the 1974 Watchtower quoted here, were in stage #4. Stage #5 had already begun at Bethel as early as late 1975 and early 1976, even though the initial definition of the time period was not about what would happen in 1975, but what would happen in the short number of years or months following 1975.
"The publications of Jehovah's Witnesses have shown that, according to Bible chronology, it appears that 6,000 years of man's existence will be completed in the mid-1970's. But these publications HAVE NEVER SAID THAT THE WORLD'S END WOULD COME THEN. Nevertheless, there has been considerable individual speculation on the matter. So the assembly presentation "Why We Have Not Been Told ‘That Day and Hour'" was very timely. It emphasized that we do not know the exact time when God will bring the end."--w74 10/15 p. 635 "It appears" that 6,000 years of man's existence will be completed in the mid-1970's." Note the backtracking (stage #4). Note even some "finger-pointing" (stage#5) in blaming considerable "individual speculation." The 1966 book (see first post in this topic) said "Six thousand years since man's creation will end in 1975." It did not say "it appears." Now, the new Watchtower didn't even want to use the term "1975" but changed it to "mid-1970's." Previously the question had been "What will the 1970's bring?" But this brings up an important caveat about stage#3 and stage#4 above. As Witnesses, we had an internal policy and external policy. So even while we could expect the more "reckless" stage#3 statements in our own special meetings from traveling overseers, circuit assemblies, and service meetings -- we could expect more careful stage#4 statements when we addressed the public in Sunday public addresses at the same assemblies or district conventions. In preaching, we were careful in such a way that we could even use language that meant stage#4 to the public while we were simultaneously able to treat it as less careful stage#3 speech. Here's a subtle example from a 1970 Watchtower:
*** w70 4/15 p. 256 Announcements ***
WHAT WILL THE 1970’S BRING? Many believe that the 1970’s will see drastic changes in man’s affairs, some hoping for the better, others fearing the worst. What is your view? Whether good or bad, no man knows for sure unless Jehovah God himself reveals it. Will he do so? His own Word says, Yes! Through his prophet Amos, Jehovah has promised: “For the Lord Jehovah will not do a thing unless he has revealed his confidential matter to his servants the prophets.” (Amos 3:7) Do not guess! And do not be unprepared! Whatever the future holds, it can work to your good if you read the Bible regularly, assisted by The Watchtower. Send today. One year, $1. Write now and receive free three timely booklets on Bible subjects. While we were not stating it for sure to the public, internally we all knew what it means that Jehovah is revealing his confidential matter to his servants the prophets. We don't have to guess. We don't have to be unprepared. This is the same idea in Sinutko's talk, saying that "we don't have to guess." ( He said: "Well, we don't have to guess what the year 1975 means if we read the Watchtower. And don't wait 'till 1975. The door is going to be shut before then.")
Compare the 1970 announcement to the same type of announcement just 2 years earlier:
*** w68 4/15 p. 256 Announcements ***
WHAT DOES YOUR FUTURE HOLD? What will the future bring you? Will it bring you peace of mind and security? Will it bring you faith and favor with God? It can! Regular reading of the Bible and following its teachings closely will bring you this and more. To ensure your full appreciation and understanding of what you read you need The Watchtower also. Study it with your Bible and receive the greatest benefit from what lies ahead. Send at once and receive three timely booklets on Bible subjects. One year, $1. This type of ramping up of the rhetoric was common. There are several more examples.
I'll stop here for now, so this doesn't become impossibly long.

Lol!
I've always liked what one father said to his daughter (quoted in one WT): "plan ahead as if Armageddon won't come in your lifetime, but live your life as if it will come tomorrow"
I apologise to those who have heard me say this numerous times before.

Yeah, that way when she sits down she sits where the camera is pointed so the video does not consist of an empty chair. They are not the first filmmakers ever to have done that.

True. This is the way it's now defined. But when did the first group die off, or do we know for sure they have died off yet? If a person can be anointed from their mother's womb or their birth, even if they did not personally realize that anointing until they were 10 or 15 years old or older, then a 113 year old person, living today but born in 1914, can be included in those persons who "saw" the sign in 1914, even if they didn't understand it. Remember that even a man like F.W.Franz who was part of the first group, and even BAPTIZED in 1914, was still claiming that Jesus presence had begun in 1874 and his kingdom had begun in 1878. He claimed that well into the 1920's. He didn't drop the first of those two ideas until 1943. The "Gentile Times" had ended because, in 1914, Jewish people would now be returning to Palestine. So NONE of the anointed "discerned" the so-called meaning of the 'events" of 1914. Therefore a one-day-old child in 1914 was just as discerning as F.W.Franz was on that particular count, and they both "witnessed" the events of 1914.
So, who says the first group has actually died out? Based on the definitions given. a 103 year old, such as my grandmother-in-law, might actually be part of the first group, and she appears to still be in pretty good health. Good eyesight, good original teeth, good hearing, excellent mental health and memory. She walks a little more slowly than when she was younger, and could leave us at any time, but she was born in 1914, and I'm sure there are older persons than her in a similar situation. 
So, perhaps persons in the second group are still being born, and perhaps Jehovah sees their anointing from the womb, or from birth. If any of these persons live to be 103, no older than my grandmother-in-law, then the generation can technically last until 2120. (2017+103=2120)  People of "this generation" that Jesus spoke of might be born today.
How far off is that reasoning?

It's a trap, @Noble Berean!! Don't fall for it!

For now 

Ooooh, second paragraph; "It's a murder epidemic" declared a Negro student in Atlanta".
LOL
Some things have changed, yet others haven't. It's like reading today's news. No wonder some say " Why,.......... all things are continuing exactly as they were......."
Page 12/13/14: "A crucial question now arises: Is there any indication in God's timetable as to how much time there is left before this system of things comes to its end? Can we know how many more years remain for this violent system of things? The fact that fifty-four years of the period called the "last days" have already gone is highly significant. It means that only a few years, at most, remain before the corrupt system of things dominating the earth is destroyed by God. How can we be so certain of this? (ouch). One way is by noting what Jesus said when he gave his great prophesy about the "last days". After he listed the many events that would mark this period, he also stated: " Truly I say to you that this generation will by no means pass away until all these things occur Matt 24:34. Jesus was obviously (ouch) speaking about those who were old enough to witness with understanding what took place when the "last days" began."  And then it goes into calculating that a 15 year old in 1914 would now be nearly 70 years old. "And remember Jesus said that the end of this wicked world would come before that generation passed away in death. This of itself, tells us that the years left before the foretold end comes cannot be many" Then it goes into calculating the 6000/1975 years etc.  "does this mean that the above evidence positively points to 1975 as the time for the complete and of this system of things? Since the Bible does not specifically state this, no man can say. However, of this we can be sure: the 1970's will certainly see the most critical times mankind has yet known..........If the 1970's should see the intervention by Jehovah God to bring an end to a corrupt world drifting towards ultimate disintegration, that should surely not surprise us"
 
 
 
 

We say Witnesses got all excited over something that turned out to be a big nothingburger. Give them the short answer - ‘Everyone is allowed one failed end-of-world date per lifetime. It is in the rules’ - and be done with it.

I agree with @Anna on this, here but slightly reworded. The Bible is indeed "clear cut" and "no progression" is needed:
Psalm 12:6: "The sayings of Jehovah are pure; they are like silver refined in an earthen furnace, purified seven times."
Man's understanding of the Bible, however, is not clear cut and does need progression.
Men need the right attitude: 
Ps 25:4 "Make me know your ways, O Jehovah; teach me your paths." Men need permission:
Matt 13:11 “To you it is granted to understand the sacred secrets of the Kingdom of the heavens, but to them it is not granted." Men need God's holy spirit:
John 16:13 "However, when that one comes, the spirit of the truth, he will guide you into all the truth" Men need to learn progressively:
John 16:12 "“I still have many things to say to you, but you are not able to bear them now." Men need help from other faithful servants:
Acts 18:24-26 "A·polʹlos...was an eloquent man who was well-versed in the Scriptures..... had been instructed....... was speaking and teaching accurately.... but ...Pris·cilʹla and Aqʹui·la....explained the way of God more accurately to him." Even with this, 
Men still fall short:
Heb. 5:11-12 "..you have become dull in your hearing. For although by now you should be teachers, you again need someone to teach you from the beginning the elementary things of the sacred pronouncements of God.." Men still go too far:
1Cor 4:6 "learn the rule: “Do not go beyond the things that are written,” so that you may not be puffed up with pride, favoring one against the other." So, men need to maintain the right attitude: 
Heb 12:5 "“My son, do not belittle the discipline from Jehovah, nor give up when you are corrected by him"

Not according to that Awake 1968, page 13/14 Quote:  "One way is by noting what Jesus said when he gave his great prophesy about the "last days". After he listed the many events that would mark this period, he also stated: " Truly I say to you that this generation will by no means pass away until all these things occur Matt 24:34. Jesus was obviously speaking about those who were old enough to witness with understanding what took place when the "last days" began.  Jesus was saying that some of those persons who were alive at the appearance of the 'sign of the last days' would still be alive when God brought this system to its end. Even if we presume that youngsters 15vyears of age would be perceptive enough to realize the import of what happened in 1914, it would still make the youngest of "this generation" nearly 70 years old today (in 1968) So the great majority of the generation to what Jesus was referring has already passed away in death. the remaining ones are approaching old age. "And remember Jesus said that the end of this wicked world would come before that generation passed away in death". end of quote
So this is the first group, and like you said, the first group is dead