Finally found my photos relevant to this. Of the pre-fastback Treks that have passed through my hands:
* '82 613, no idea, no photos of the BB shell, bike was stolen ca. 1990
* '84 420, Asian contract build with seat-tube serial number, N/A
* '82 710, re-sprayed and re-branded with '84-ish livery, a VERY faint strike of three characters (the thick respray doesn't help), possibly NK3? NR3?


'82 412 with some non-stock build quirks. Couldn't find the maker's strike, but the BB shell indicates a Tim Isaac design (vintage_trek claims the 60TSI is "rare" (shrug)):


His & Hers '82 730s, once again no maker's strike, but these two have the "58TSI" BB shell stamp.

I met Mike Appel a year or so ago; he answered my CL ad selling a seat post. Rode the '82 412 to meet him. Affable fellow; he told me he left Trek in '81 and came back some years later. He didn't know about the vintage_trek site or how the photo of him and Dick Nolan was featured on the home page. I totally spaced on asking him about his more recent frame building work.