In the front of the book Jehovahs's Witnesses In the Divine Purpose (1958 WTB&TS of Pennsylvania) it has a list of dates beginning with 1870 when C T Russell begins studying the bible with a small group and ends with the date 1919 the release of the Society's officers from prison.
I believe 1919 is the date that is given as the date that 'From atop this celestial chariotlike organization Jehovah commissioned this dedicated, baptised , anointed class of servants to speak to all the nations in His name. Thus like Ezekiel , they became Jehovah's witnesses.' (Nations Shall Know That I Am Jehovah-How? 1971 WTB&TS) and you have the faithful and discreet slave from this date.
The next date listed in the front of the Jehovah's Witnesses In The Divine Purpose is 1877 the date the book Three Worlds was published and 1914 was identified as being the end of the gentile times.
In the Watchtower October 1 1983 page 4. It says.
'What do you mean by spiritual paradise? you ask. Put simply; An organization of Christians who have made over their personalities to conform to God's requirments and who are united in his true worship may be said to be in a spiritual paradise.'
As they have never changed the date of the end of the gentile times since 1877 and since 1919 the organzation of Jehovah's Witnesses has grown to what it is today in what has been identified by the witnesses as the last days in fulfillment of Isaiah 2:2-4
'It must occur in the final part of the days that the mountain of the house of Jehovah will become firmly established above the hills and to it all the nations must stream. (NWT)
Then I would present this as my basis for obedience to the GB.
( just thought i'd flesh out my earlier post)