[TUHS] UNIX Usage for Bell Telecom Typesetting

Good evening folks, I'm doing some research lately into the typesetting style apparent in the various UNIX System V guides I've scanned to archive.org. Their typesetting style is unlike that of the MM papers published with 3.0 and 4.0, but the contents seem to have continuity with the text in these collections. Well, in my searches sometimes telecom documents from the Bell System come up too and in materials from the 70s and 80s I started noticing that familiar typesetting in telecom stuff such as that hosted here https://www.telephonecollectors.info/index.php/browse/bsps-bell-system/bsp-… The earliest example I could find is 1969, so certainly at least a publication style that predates UNIX, but what I can't tell from my searches alone is if this style implies some non-UNIX typesetting system through and through or if there was a macro package dreamed up at some point between 1969 and 1982 that was in place by the time of the System V documentation. Just to detail specifics of the publication style, the commonalities I've found are the use of specifically bold numbers for page numbers, having the doc title and call number in the outer upper corner of pages, and just the fonts themselves look very similar. As an added note, the fonts used in the telecom documents and System V guidance documentation also resemble those in the copyright statement pasted on the cover of the extant PDF of the fifth edition UNIX manual. There is also some resemblance to the visual style observable in USG Program Generic and adjacent documentation (for instance the 1976 kernel description of PG 2 or the MERT 0 documents). This typesetting style is not seen in known research, CB, nor PWB until 5.0. Was there some separate typesetting system used in the broader System that, say, WECo may have taken up when they took over documentation between 3.0 and SVR2? - Matt G.