This is a little bit of an aside, but I've had some experiences with 'nail down' models.
John is right - stores didn't want you buying those. While living in Denver, I saw an appliance store run a weekly ad in which in 1981/1982 they were always advertising either a GE BOL or a Frigidaire BOL for $249. This is how I became fascinated with the the one-knob wonder models, and clearly, the GE was the much better washer of the two offerings.
Within the last two years, I tried to buy a one cycle Roper DD washer - it had even only a single solenoid fill valve. It was on every floor of Charlotte's Queen City Appliance for $199. Matching dryer too. I nearly had to create a scene to get the salesman to even consider selling me one. It was frustrating. When I realized I truly didn't need it, I backed off.
Law requires, as John eluded to, that these models be available for sale, or an alternate be made available, if they are advertised to be on sale, etc. I stopped one day in fall 1982 at that store on my way home from school, just to see what the GE was - it was a non-FF basic single cycle standard capacity GE. There were blanks in the two toggle switch holes on the left side of the console. I stood there looking at them, a salesman came up and didn't even say hello, but said "You don't want that model" or something like that.
What I paid more attention to is that Sears didn't offen have a washer that could compete with that sale. They had the 24-inch belt-drive at this time in the catalog for $249, but that required shipping. Once in a while they'd advertise the one-knobber for this price, but usually just a weekend only.
They may not have intended to sell many back then, but if recent Craigslist evidence is any indicator, the 1990s version of this one-knobber sold like hotcakes in their various Kenmore, Sears, Capri, etc. versions.
True too about the large capacity machines without a water level adjustment - Sears did that in a number of models - 1972, 1976, 1980, and 1982 to name a few. It would take me some adjusting of habits to use a large capacity machine to its fullest without wasting water, if I could not adjust the level. I have the 1980 model - it needs a full resto but it will one day get it.
One thing about Sears - they always had a one-knobber / Nail down model in the catalog. I presume they could be had that way with less hassle than from a salesman.
Gordon