Dave -
Three speed belt-drives were made for at least 10 years, from 1964 in the '64 Lady K to the 1972 hold-over Lady K which was made into early 1974 when the revised 1974 Lady came out with large capacity but only 2 speeds. There were a few other non-Lady K models which were 3-speed during this time as well.
Whirlpool machines may have been produced sooner and later as well, but I am not as familiar with their 3-speed models.
Gordon
Three speed belt-drives were made for at least 10 years, from 1964 in the '64 Lady K to the 1972 hold-over Lady K which was made into early 1974 when the revised 1974 Lady came out with large capacity but only 2 speeds. There were a few other non-Lady K models which were 3-speed during this time as well.
Whirlpool machines may have been produced sooner and later as well, but I am not as familiar with their 3-speed models.
Gordon