It's been a while since I worked on this for several reasons, mostly me doing other things. Having finally gotten around to it, I find a set of circumstances that I can't explain.
We ordered the brushes from a local sewing shop. While we had the micrometer and the old brushes, along with measurements, they decided to order them according to what is supposed to fit a 201 with a potted motor.
The brushes that came in don't seem to fit. The brushes I removed quite easily and smoothly once I got hold of them, measure .22 inches each direction. They seemed a very good fit and are square in cross section. You can actually see a close-up of the square brass tube in a previous picture.
The brushes which arrived are .155 inch by .186 inch, rectangular in cross-section. I dropped one of the smaller brushes into the larger brass tube in the motor brush hole, just to say I actually tried it. The brush will almost rotate within the square brass tube. Clearly too loose to even try, in my judgement. A loose fitting brush could break up and damage the motor. And be difficult to get out, again.
So, ether we got the wrong brushes or this is an unusual motor. I certainly wouldn't want anyone to take a brush out just to look, since it's best to not disturb their seating. But can anyone off the top of their head confirm that brushes for a 201-2 are square in cross-section?