P4120701 Small Block Mech Tach drive

Oh no doubt good distributors. Like I stated there is just mechanical advance in it and either it is gummed up or some one welded the weights to use a external trigger on it, why no idea I would have used another lower cost distrib to do it. Can you turn the rotor a bit while it is in the car to see if the advance moving at all? Also have a pick of it from the top down by chance?