We took a family trip to that region of Ohio many moons ago. Of course I went to the museum. Still have my "Hoover 100th" shirt that Tom have me when I toured the museum. I have pictures somewhere...
There are no motor mounting screws nor a brushroll.
The issue I had with mine was that the bottom "floater pad" was rusty and not perfectly smooth. This allowed air to seep out and it had a hard time floating. Sand it smooth on the very bottom, and ensure the motor is getting ample airflow.
I have found that UPS is a bit of a rip off. As much as everybody is expensive, Federal Express is the best option, in my opinion. They cost close to the same as the USPS, but are far more careful with packages.
Go see Chris at C.S. Vacuum in Oneida. He does fantastic work on cleaners and has close to 5000 in his trade ins. I'm sure he has a few decent model 28s...it is his favorite machine...
Brown would be a rebuilt model during the run of the Olympia 1. Brown or chrome PN4 with a cream sheath set and an electric woven hose, cream with brown chasers. Beige cord.
The Hoover 150 is my all time favorite! I spent an absolute fortune getting one that was in beautiful shape and had been mechanically restored. Well worth every cent!