I don't recall this thread from four years ago, so I am reading through it the first time. First, I have a copy of the 1950 first edition of the NWT Greek Scriptures and it indeed has 'the' in the verse at Matt 24:45, as dsp demonstrated. If there was some limited edition with 'a' in that verse, I haven't seen one. I doubt it even existed in print. I think Losch was simply mistaken, or at most was referring to some pre-publication draft that he may have access to.
What I think this thread discussion is missing is that at the time of translation, the main 'enemy' of the WT were the Bible Student groups (the 'evil slave class') who believed that Pastor Russell was 'that Servant'. This was a big issue from the '20s into the '60s, and there was a lot of bantering back in forth between the writers of the WT and the writers of the various Bible Students. I used to have some of Paul S L Johnson's books, and you wouldn't believe how many pages he devoted to this inane subject.
The WT belief they espoused at the time (1950) was that the 'faithful and discreet slave' was not an individual, certainly not Russell, but rather was the faithful and discreet slave 'class', which they interpreted as entire body of anointed, all of them. The application of this verse to the Governing Body only, and not to all anointed, is a relatively recent change in doctrine.