I am restoring a MH-50. Is it supposed to have a resister before the coil?
Yes, your MH-50 should have a coil with an internal resistor. No external resistor. I suspect someone replaced the original coil with one that requires an external resistor. Your local NAPA dealer should have the correct coil, it is the same one used on the Ferguson TO-35 with a 12 volt electrical system, and a Massey Ferguson 35. You should also be able to purchase a 12 volt coil with an internal resistor from many after-market tractor parts suppliers.
If you are unable to locate one let me know. I can provide you with specific sources, and part numbers.