They have some distinctive markers to make them easily identifiable. Not sure what these markers were for the closed cans, but nowadays they have openings so one can see a ring of a certain colour on the rotor. That ring tells the scrutineer if you have changed the rotor or not.
Not sure there is any other difference. In electrical parameters I am pretty sure there isn't as it would make no sense for any company to make different motors for different purposes but with the same number of winds. It's much easier to make different rotors.
Team Greasy Weasel
The best upgrade to any car is some driver skill.