Wow, the machine I was referring to was in operation in 1979 at a small suburban paper of a few thousand in Texas so presumed it was in wider use.
I recall reading that Miller was trained up in printing- is that right?
In the late 70's, mainstream press was moving to optically set aluminum or steel "foil plates"... so TSR, Avalon Hill, SPI, Yaquinto, and GDW all were buying up used linotypes (or it's competitor, whose name I'm too lazy to look up) as local printers deleted typesetter.
Note the following methods were ALL in commercial printing use in the mid 1970's and early 1980's, in changing proportions:
typed then optically mastered
Hand-written then optically mastered
Typeset, single printing by hand, then optically mastered
Typeset, print from assembled lead strips
Typed stencil (for mimeography)
Typed or handwritten inked master (ditto machine)
Note that typeset in this context means two different processes - manually fitting individual letters into printing frames, or casting lines of lead to form a contact press. A third was in minor use: typewriting an aluminum or steel or copper sheet for intaglio/lithographic printing.
Of these, individual letter cast and lead-cast are the only ones where the imprint is raised noticeably. Intaglio and Lithographic are both normally press paper into wells of ink.
While I know a shop in Anchorage was still using steel letters in frames as recently as 1983, it wasn't for English... it was printing in Cyrillic for Yupiq, Church Slavonic, and Russian. (Yupic in Cyrillic was dying out back then... Now, it's a historical footnote.)
I watched optical setting of stencils mimeographs in 1977 - in my elementary school. Meanwhile, my dad used a stencil cutting typewriter for some handouts at his job that same year. Also for mimeographs.)
I've high confidence that CT was optically set from linotype in-house mastered one-offs.