When was it first introduced that the Watchtower Organisation was chosen in 1919? I expect this was something first published under Rutherford, as a way of making his leadership more important than that of Russell, but would like some evidence to back that claim up.
When was the significance of the year 1919 first stated?
Good question. Will check A People For His Name, later as that has quite a good account of how doctrine developed over the years. (I'm at work at the moment)
As far as I can tell, this was fairly blurred for a long period - and probably still is. Rutherford's book, Riches, (1936) introduced the idea (using the principle of types and antitypes) of an "Elisha" work beginning in 1919 following on from the "Elijah" work of the preceding period.
So when was the "faithful and discreet slave" appointed? That was never clarified - this was my summary in 1996:
"The doctrine of the "faithful and discreet slave" allows room for the view that the Watch Tower movement, as constituted under Russell's leadership, was already Jehovah's organisation, and that its commissioning for the prophetic role of the antitypical Ezekiel did not amount to its first becoming Jehovah's organisation." (Counting the days to Armageddon, p121.)
The trouble was that every item in Russell's end-time calendar had been reassigned a date in a new calendar beginning (instead of ending) in 1914. But Russell's understanding of his movement's place in the divine plan could not similarly be transferred to the new era without throwing away the foundation on which Rutherford had built. So this problem was left unresolved. And it looks like the Wise Old Men are only now getting around to tidying things up. To get away with it they will need Russell to be completely erased from their history.
I found a reference in Salvation (1939) which says on page 67-68 "Jehu in the performance of his duty and commission pictured Jesus Christ, the great Executioner and Vindicator of Jehovah's name, and also the faithful followers of Christ Jesus and particularly "the remnant" from and after the year 1919."
1919 is also mentioned on pages 145 - 147 in relation to the releasing from prison both literally and from Babylon.
This guy has some interesting info and exposes how Russell taught the WT had already been chosen in 1874 not 1919
Since things are usually "discerned" over time it may be difficult to determine when this decison was fully complete. However, I have found the August 1 & 15, 1930 Watchtower to be enlightening as it claims that prophecy could only be understood after the Lord came to his Temple in 1918.
These articles re-interpret the Terrible Image in Daniel and its various metals as being elements in "Satan's Organization" and claims that the then previously believed Adventist interpretation (with each section representing a world power) was inaccurate but it was to be expected because the correct interpretation could not be unkown until after 1918. Note that "great signs" were part of this process:
WT Aug. 1, 1930, Paragraph 45: "When the Lord came to his temple in 1918 greater light began to shine into the mind of each one of his devoted ones who have been brought into the temple. It was about 1925 that the faithful discerned the fact that the kingdom had begun and that Satan had been cast out of heaven and now must confine his operations to the earth. The two great signs or wonders in heaven appeared unto them and were then understood by God's people for the first time.
46: It therefore seems to be impossible that even the anointed of the Lord could have had a proper conception of the 'terrible image' of Daniel until after the coming of the Lord to his temple..."
I would try Edmund Gruss book
Try w30, July 15, p. 214, par. 25 onward.
25 The days of pruning arrive and the separation begins and progresses. It is well known from the facts that from about 1875 to 1918 all the Lord's people walked together. In 1918 and 1919, at the coming of the Lord to his temple, all were subjected to a severe test. Why did the Lord do that? The answer is that this was a severe pruning experience, that the faithful might be made manifest and might bring forth more fruit. (Vs. 2) Shortly following the end of the World War, and the coming of the Lord to his temple, he gave the commandment to the pruned ones, or disciplined ones, and to these said: "This gospel of the kingdom shall be preached in all the world for a witness unto all nations: and then shall the end come. "-Matt. 24: 14.
26 Those who had been faithful and diligent in obeying the commandments of the Lord and had thus shown their love for God and for Christ, upon them the Lord then bestowed even greater love. To these approved ones the invitation was given to 'enter into the joy of the Lord', and this is in harmony with the words of Jesns: "As the Father hath loved me, so have I loved you; continue :re in my love. If you keep my commandments, ye shall abide in my love; even as I have kept my Father's commandments, and abide in his love. These things have I spoken unto you, that my joy might remain in you, and that your joy might be full." (VSS. 9-11) God has taken Jesus and his body members into partnership with him for the kingdom. Those on earth have some work to do, and they are made members of the "faithful and wise servant". Their work is then to bring forth or bear the fruits of the kingdom, and this they do by diligently looking after the interests of the kingdom.
I'll look to see if I can find earlier hints ...