Erik -
I think the toast and platinum colors lasted a bit longer than two years, as I've seem some 1986 and 1988 model Direct Drive washers in those colors. There was even a platinum machine on here in the deluxe forum a few months ago that had a color-coordinated gray control console, which would make it a 1990s model.
The basket mounted lint filter debuted in some later versions of 1981 and 1982 models as a running change in those machines which were initially equipped with tub mounted filters. I believe this happened in 1982. The 1983 models had them from the beginning.
I used to think the tub mounted, pump flushed filters were much more effective than the basket mounted filters, however I have never had a lint issue with my 1986 belt-drive machine which I bought new. Recently, I have used a few belt-drives in my garage that were not permanently installed. I drained the standard rubber drain hose into a 3-inch diameter, 20-foot plastic drain pipe that I dumped into the yard to water the grass. The first machine, my 1980 fancy 80-series, has a tub mounted filter. It leaves a characteristic deposit of lint in the grass where I drain the washer water using that long hose. The next machine, a 1982 Kenmore 60 with manual filter did not leave any lint in the grass. Surprisingly, the third machine is 1986 version of the very same machine as pictured above, with the basket disc filter. It leaves as much lint in the grass as the 1980 machine. I was stunned to see that.
As to how the basket mounted filter is cleaned - it seems to me that the pump draining action, not the spin, is the key. ALL machines that have a basket mounted filter use a specific 2-port pump which is different than the 2-port of old. This pump debuted in 1974 on some models with the manual filter. That particular pump works dramatically faster than the older pumps and used to cause a lot of laundry room flooding as the sudden rush of water in the black rubber drain hose caused the hose to fly out of the standpipe or sink, flooding the floor.
On the 1981 and 1982 models that originally had a tub mounted filter, the pump was changed to a new two-port, non-recirculating pump when the disc filter was added and the models received a running engineering change. This pump works in one direction only (the old two port operates in two directions), so on suds-saver versions of these machines, the original tub-mounted filters were used up to the end of the belt-drives, along with the older recirculating/reversible pumps. The machines needed the old-style pumps to bring the suds water back into the machine. My theory is that if the fast new-style pump was not needed to make the basket filter work, the suds models would have a basket mounted filter too. WP would not have kept the old filters and accomodating outer tubs available if they could have been eliminated from production.
Next time I run a basket mounted filter model attached to my yard-drain set-up, I'll be sure to see when the lint appears in the grass - either during the drain or during the spin, then I'll know for sure!
Gordon