Sorry, Sheldon . . .
. . . these units are not popular today. Their main problem is that they take about 1.5 to 2 hours to do a load of laundry. At the time they came out, housewives were used to doing a week's worth of laundry in one day -- wash on Monday, iron on Tuesday, etc. It was hard for them to get out of this habit, therefore doing several loads of laundry in a day took all day long.
Today, however, people wash clothes several times a week, and these machines might be more popular now than when they were first introduced.
Combinations were made by Whirlpool (Kenmore), GE, Easy, Norge, Speed Queen and several others none of which are made today unless you could buy a Sears Kenmore through the Sears catalogue.
I can't help you with the value of this machine. I'm not good at bargaining. I see something I want bad enough, I buy it. But I doubt that you'll get rich by selling this Duomatic. I just hope that whoever gets it is interested enough to use it and keep it in good condition. Mine is a 1959 model and I've used it for several years with no major problems. It's not my daily driver, but it gets its share of use along with my 1944 Baby Bendix (one of the ones that has to be bolted to the floor or it would walk).
Best of luck to you with the Duomatic. If you have any other questions I could answer, I'd be happy to.
Jerry Gay