William Schnell, in "30 Years a Watchtower Slave" (chapter 5) wrote about how the Watchtower Society was "bent on eliminating the last vestige of individual thought and action within her ranks".
Using an increasingly strained extension of the concept of "types" and "antitypes" of Bible characters, Rutherford and his buddies set themselves up as the "Faithful and Wise Servant Class", to whom all goods were given, in a bid to eradicate completely the old Bible Student belief that CT Russell had been the "faithful and wise servant".
After that came the "Mordecai-Naomi class" (the last members of the 144,000 anointed on earth), then the "Ruth-Esther class" (a later, younger class of recruits when it was discovered the door to the heavenly class hadn't actually closed), then the vast "Jonadab class", over whom they would all rule. Schnell wrote: "Note that each class emerged on a lower strata, and the lower the strata the larger the numbers."
There was also the "evil slave class", and if you can be bothered reading Watchtowers from the 20s and 30s, you'll encounter many, many more: I started making a list of them at some point and it was both tedious and absurd.
Ray Franz, in "In Search of Christian Freedom" (p.166-7) wrote a fairly devastating critique of the Society's "class" concept as they applied it to Luke 19 and Matthew 24. He says that at Governing Body meetings he argued for consistency: since the "faithful slave" became a class, shouldn't there also be a "ten-mina class" and a "five-mina class", a "many strokes class" and a "few strokes class"? Where would it end? In the end, he said, the parable was being perverted: "Rather than serving as an exhortation to modest, faithful service to one's Master and one's fellow servants, it is used principally as a means to demand unquestioning submission to the Governing Body's direction."