I.B.S.A. were all about witnessing to, for ,and about Jesus Christ and not Jehovah. , C.T Russell started the magazine titled " Zions WatchTower and Herald of Christs Presence" in the late 1870`s .
Stating that Jesus Christ had appeared invisibly on his return in 1874 and was now present in the heavens.so according to them at the time they could rightly say as the WT pronounced they were heralding Jesus Christs presence then.
Charles Taze Russell and his followers were witnesses of Jesus Christ and not witnesses of Jehovah.
The Christian Greek Scriptures /New Testament are full of the prime purpose of Christians is to witness about ,too, and for the person/ name Jesus , that has been given above any other name either in heaven ,on earth ,or under the earth Phil.2:10
It was only the usurper of C.T.Russell Joseph Rutherford who hijacked the religion and made it a Jehovian/Old Testament religion shifting the emphasis away from Jesus Christ and putting it on a catholic name of the "Old Testament God Jehovah" invented by a 13th century monk using the four letters of the Tetragrammaton into Latin and adding some vowels to come up with the name Jehovah.
No where in the Christian Greek Scriptures the New Testament are followers of Jesus Christ told to be witnesses of Jehovah ,however countless times at least (20+) they are told to be witnesses of Jesus Christ.