In 1927, Rutherford said that the "Coming" (erchetai) in the parables of the "Talents" and of the "Faithful and wise servant" related to Jesus coming to the temple in 1918. That was the time the "Servant" class was created - comprising Jesus as its head and all spirit-anointed as the body/feet, although it could also refer to Christ alone or to the body/feet alone. It was in this way that Rutherford related the relationship between the "Faithful slave" and 1918. (He also said that the "Evil slave" were those people who had fellowshiped with him but now stood in opposition.)
Whereas Rutherford saw the Coming as a past event, the current WTS leadership says it refers to a future event that is associated with the Great Time of Trouble and Armagedon. Obviously then, they cannot relate the "Coming" to the setting up of the FDS. Rutherford's coming was an invisible action taking place in the heavenly temple, the current WTS teaching is completely visible, even violent.
The date of 1919 appears to first arise in the very early 1970s. At that time, and until 2013, the evolving Governing Body was a representative of the FDS class - the "spirit-anointed", little flock of 144,000. As I have said, Rutherford also saw it as a class.
However, from October 2012, and as announced in the July 15, 2013 Watchtower, the GB has expressly stated that it now limits the expression to itself.
Until 1930 at least, Rutherford's Presence (parousia) was confidently fixed at 1874.
Doug