two out of three ... the jet was a 707-131B; the original schedule was 2x/day, something like:
STL-SEA lv ~0830 ar ~1100; SEA-STL lv ~1300 ar ~1900

STL-SEA lv ~1745 ar ~2015; SEA-STL lv ~0030 ar ~0615

after taking delivery of their first 767s in late 1982 / early 1983, TW added a third frequency:

STL-SEA lv ~1500 ar ~1730
SEA-STL lv ~0645 ar ~1300

the 767 was on the evening westbound and morning eastbound, I believe mainly as a continuation of STL<—>LGW; between ~1988-1995 all three frequencies were operated by MD-80s most of the year, with the 767 (occasionally an L-1011) only appearing during the summer