...even the last of the 5513 models in the 80s originally had thicker fonts than we see on replacement inserts from the 90s and later.
For example, Rolex Lumi replacement insert (ca. 2000 and later):
And an 8.29mil SN 5513 (ca. 84-85):
(Pic from the Archive posted by jon3110)
More here about the true Thick Font Sub inserts from a Classics post by the great M. Pisani: