The magneto is not very complicated. If the points are clean and have low resistance when closed, they are opening and closing, the wires are continuous and not grounding out anywhere, the flywheel is still magnetized, and the laminated steel core of the coil almost touches the flywheel on both sides of its center, then you have a bad component: condenser or coil.
When you tried a different magneto, do you know the replacement one worked before you removed it? Are you sure it was grounded properly when you installed it? Did it work again when you put it back in the original mower?
There is no witchcraft involved here, the system is rather simple.
I agree with you grumpy and would first start with the replacing the condenser first then move to the points before going to the most expensive part the coil because it is not that often the coil breaks down on the old victa's.
