i found some interesting info
in my parts manuals i dug up for frigidaire. this pertains to model numbers.
i have a dwcdtr and a dwcdmr.
frigidaire said the dw refered to dishwasher (obviously) and the cd would be custom deluxe. i would be imperial, ci would be custom imperial etc.
m is for mobile
u is for undercounter
t is for top loader
sd is for standard door kit
fk is for framing kit
and the last letter refers to the year it was made. they list l n p r and t.
they said p was 1969 and t was 1972
so dwcdtr would mean custom deluxe, top loader r series. if p is 1969 and t is 1972 i am guessing r is 1970 or 1971.
dwcdmr would mean custom deluxe mobile (front loader i would guess) of the same period, circa 1971.
don't know if this helps anyone but i thought it was intersting trivia out of the frigidaire service tech manual.