General Motors and 'optional' second rinses
After a quick check of the 1964 GM Frigidaire doctrine, they do present a second rinse option within the timer sequence chart, therefore putting GM currently at the front of the optional rinse game about the time LBJ was taking over office.
A second rinse option was not available on pre-66 Lady Kenmore machines. I would suspect the 'Mark' line of Whirlpool would have been a year or two later considering Sears was always holding out on earning as much as possible on the extra options as they could.
The earliest I can figure GE had it was with the 1967 control panel revision. A brochure posted last year (link below) shows the extra knob for the switch, so I suspect that was the function. I've seen it on 1968 and 1969 TOL panels, so I'm making an assumption that it was available a year earlier as well.
Frigidaire had two deep rinses permanently programmed into the timer, starting with the WJ-60 in 1947 through the WO-65, ending with the WO-65-2 and it's overflow rinse in 1952. The second rinse was anything but optional by choice on those early Unimatics, but instead automatic. Westinghouse and Bendix also had multiple rinses, however that would be expected with those machines being primarily front loading.
When it comes to some of the other players (Norge/Westinghouse TL/Hotpoint/Blackstone/EASY/Kelvinator/Philco TL, etc.), I'll have to defer to other members on the board.
Ben
For some reason, I find the cover offensive:
www.automaticwasher.org