>>If you had a typist who could do centering using proportional-spaced fonts, I'd like to meet her/him!
Absolutely correct. You HAD to use mechanical typesetting devices like the Varityper or the IBM composer for this.
Using Varityper or a photo compositor would create the effect except there was one little problem.
It regards the font. TrueType Times New Roman is a variant of the font created in the 1980s. Slight, subtle differences, but noticable to someone really adept at specing type.
The document was processed using that particular font.