It cleaned up really good! Yeah the fact that that tag on the motor has a blank spot to stamp in the voltage number makes me think it was a universal motor. It looks like the population of the city it came from, Granite City, IL, only had just over 9,000 people by 1910 and afterwards until 1920, so it does look like it was a farming town and they would have not had Edison service until later on.
The Bee Vac I have, it had a similar story, it is on DC farm voltage, and it came from a very Amish-centric town in Wisconsin with a population barely of 10,000.