Very interesting I thought for sure you would find some play in the shaft.
A lot of corrosion inside the distributor, I hope the mechanical advance is operating properly.
This miss you have are you certain it is only at idle rpm?
Not sure if it´s corrosion or just dirt, but the advance is working properly when checking with the timing gun, and it revs smooth and freely without any problems if I push the throttle, the slight "misfire" problems is only at idle.