Charles -
From what I can see in the WP catalog, there were actually FOUR 1976 90-series dryers under the Lady K dryer. There was a '901, a '911, a 921, a '931, and a '941. The 66941/76941 presumably being the Lady K. The 931 used the same "timer" (dryness setting knob) as the TOL, then the other three used varying mechanical timers. I am not certain what those dryers actually featured without consulting the catalogs.
There were no 1977 variation 90 series dryer models, and only one 1978 - a 68911 / 78911. Most of the '76 models likely held-over for a few years until the huge 1979 line debuted.
Gordon