6v coil ???

regarding a coil check, I would check the spark at the coil high tension lead by removing the center connection from the distributor cap an attempting a start This will show the overall condition of the primary system and the coil and then by checking the point gap and point condition and finding them to be right, you could infer a healthy coil if you had a fat bluish spark and infer an unhealthy coil by a weak bluish, orangish or yellowish spark.
Not much in the way of electronics in these tractors, just 1940's technology Kettering type ignition system.
I you haven't all ready got one, investin a Ferguson shop manual, owners manual and parts manual. the shop manual will provide you with a lot of info on how the factory installed systems work and the parts manual will show you the parts breakdown which is very helpful. the owners manual will tell you how to use the machine properly. Then there's this forum wth a bazillion years of cummulative experence just waiting to help the new guys and gals.(Yep there are females that get hooked on these old machines so it's not an exclusive "guys only" world.)The archives is a good place to go because the questions in the forum are almost all repeats of previous questions. You can find alot of answers to common problems in the archives.
If you were my neighbor, you'd earn the answers to your questions. I have a small ranch in the Northern Rockies, my TO-30 hauls my pipe trailer and plows snow, etc and I'm pretty busy, so to catch me and ask a question,you'd have to help me!!

I'd suggest you use the coil until it fails and then buy a coil for the voltage your system is. Then you'll know. If there is a part number on your coil, a good parts man may be able to identify its aplication.

Gerald J.