The Minnesota was a machine sold through the mail order of Sears & Roebuck. The Minni, however, had many different suppliers and came in different models (A through K). Some were made by Standard Manufacturing of Cleveland, others by Domestic of Buffalo, and still others by Davis.
For awhile now, treadle machines have not been very easy to sell. I've seen them taken apart to sell better. (cringe) Drawers for 35 dollars each and ironworks for 50 or more when a complete machine and cabinet can't bring a hundred. But this is changing. At least it's changing where I live.
There seems to be a bit of a movement by some of today's youth as they seek out and find alternative energy machines. A pre-existing treadle doesn't need gas or electricity. It doesn't cost anything to operate - and it's already been made, so resources do not need to be spent making a new one. If needles and bobbins can still be found for your machine and if it sews... then your chances of selling it are doing better now than in the last ten years. But I would advertise it that way: I'd come out and say it won't 'add to your personal carbon footprint' - and that it's healthier for the environment and etc. I mean why not? The person looking for one just because of those reasons might read it, and that's the perfect match: a person that's going to use it to sew.