Don’t let the coil throw you a curve ball. It has 4 not 3 wires. Each winding of wire has two ends & you have two windings per coil so you have 4 wires.
Two from each winding go to grounding terminal & the next goes to the points connection & the last is the plug wire. Johnson made these coils without connecting the two grounds inside so the two come out. Only difference except the magnets are on the inside of magneto not on the flywheel.