.5 ohms between all three leads iirc. Still with that discoloration I would replace or have it rewound unless all the riding is on the back 40.
On a long trip with my daughter to Las Vegas I had the regulator go bad on my FJ1100 in Bullhead City, AZ. With no replacement alternator anywhere near I wired in a 1970's Chrysler mechanical regulator and finished the trip. From then on I don't ride with aged or questionable charging components.