Ford 4000 battery question

[meby]

I was looking at my fil tractor today and i'm confused. The negative terminal cable from the battery is hooked up to the starter motor solenoid and the positive terminal cable is hooked to the starter motor mount bolt, like it was being used for a ground. Its been hooked up this way for years. The tractor isn't that old 1975, I think. Is this a positive ground system? tractordata.com lists it as being a negative ground system. What am I missing?

[delsilver]

Something that new should be a negative ground system. One way to check is with a volt meter, put the positive lead on the positive terminal of the batery and the negative lead on the frame ground. If you get a positive reading you have a negative ground, if you get a negative reading it is posive ground. Note this will be easy to see with a digital meter but if using an analog you will have to watch to see if the needle trys to go negative as it can't actually record a negative reading.
Del