Another question from my MK4/90+ rebuild I am afraid. It is fitted with an AC rev counter drive on a plate in line with the standard platform MM2 mag. There was no drive to the rev counter tab when I stripped the engine, so my guess is it was intended to be driven by a special longer nut with a slotted head to replace the standard 170104 nut on the mag shaft which Joe Lucas seems to have made a 3/8 BSF thread . Did this nut need some sort of pin to stop any tendency to undo? or was there some sort of cage to drive the counter from below the nut?