Hard to tell, it's a messy area to sort out, but you have red herring in Davis models if you care to search for info. I assume you mean Minnesota A, and it was a brand Sears used on machines made by Davis. According to info on ISMACS Davis started making machines for Sears around 1899 and the Minnesota A was probably in production until around the years of WWI. This is a rough estimation of this model. t was basically a version of Singers 27 (127), and it had a long life under various model numbers, way beyond WWI. It is hard to tell when the "A" model went out, and if you compare to other machines, you will find variations on this model.
If you post a picture you might get more info. I don't think there is a list of serial numbers for these, but you can always do a bit of detective work and compare to other machines. It's not worth a lot, mostly to those who fix it up and use it. I also assume the electrical motor is a later addition, maybe even the carrying case. They came as treadles or hand cranks in portable cases.