Very early on, McCormick Deering/International Harvester outsourced magnetos on some of their early engines and tractors. Our early 1020 tractor was originally equipped with a Dixie Aero Splitdorf. Some of their early stationary engines used a Webster,Accurate Engineering,American Bosch and later Wico including the reciprocating EK and rotary A. Some tractor models were available with a Robert Bosch FU4 for export or by special order. International in my opinion made some very fine and hot ignition equipment. Many early International tractors have their original magnetos.
One early product was the model E4A. It was used in the 1920's to early 1930's on the 1020, 1530 and others. It was originally offered with a a Splitdorf type manual reset impulse and was later equipped with a more robust automatic impulse. It was a wound armature design and much hotter than the Dixie. They used a design similar to Bosch and Eisemann with the points and condenser in the ends of the armature and a horseshoe magnet, collector brush and spool with a safety gap.
Problem areas were the usual lack of maintainence, too much Oregon Rain in the wrong places, corroded points,coil insulation seepage and condenser failure. These mags seemed to fire and run in spite of it all.
Later came the F4, F6 series. Enter the modern age. These used a more modern design with a stationary coil and condenser with an enclosed more robust impulse coupler. Fewer moving parts and less maintainence. Many got no maintainence yet continued to operate. These are very hot and reliable and still fairly well supported.
The next development is the H series, like the H1 used on LA, LB stationary engines and the H4 used on tractors. They used the same coil and condenser as the F series but different points. They employed a more modern rotating magnet that made them good and hot. Problem areas are the usual, lack of lube and petrified grease, leaky condensers, corroded points and occasionally a bad coil.Sometimes the impulse pawls and pawl pins would wear causing the pawls to drag and rub on the front of the magneto housing. To pull the impulse coupler off the F and H series you need a puller that threads into the front of the coupler. If you grab the outer edge of the coupler with a puller, it often breaks. More about that later.
The Farmall Cub used the model J4 magneto. It was a very light duty device and used a special mounting flange. More on this one to follow.
One problem that torments those in the restoration process is the ignition system wiring on the farmall tractors. Some were equipped with distributors and others with a magneto. Sometimes things gets modified over time and cause confusion and grief. In either system be it a magneto or distributor there is a single wire that comes from the dash area/instrument cluster and ends near the front of the engine. If it was originally a distributor equipped tractor, this wire connects ignition coil to the hot lead to run and disconnects from power to stop. If this is originally a magneto equipped tractor, this lead connects the terminal on the side of the mag to ground to stop and disconnects from ground to run. If a mag is mounted on a tractor originally configured for a distributor and this single wire from the dash is connected to the mag it applies power to the mag. This typically burns up the points and coil and discharges the magnets in the magneto.