"Is this Michael the resurrected, glorified and enthroned Jesus Christ? Yes. [...]
"Before 2 B.C. God’s only-begotten Son in heaven was called Michael, this name meaning “Who is like God?” [...]
"On earth it was not even hinted at that he had been Michael in heaven and “one of the chief princes.” [...]
"When he died as the man Jesus Christ and was resurrected and went back to heaven, what was his proper name? [...] He resumed his heavenly name Michael."
(Watchtower 1960 3/15 pp. 184-188)
"The Bible evidence unmistakably establishes that this heavenly prince Michael is God’s Son who descended from heaven to become the man Jesus Christ on earth and who returned to heaven after his resurrection from the dead and sat down at his heavenly Father’s right hand."
(Watchtower 1960 4/1 p. 217)