I agree with SteveSr: The newer coils have a PIC microprocessor in them...(and lots of other stuff now days use solid state devices buried inside and sealed)
Not much learned here for me. (and I've seen the old style ignition system coils several times test ok using a test meter and ignition coil/Magneto tester and not work correctly on the equipment.) (weak or erratic usually) I've got all kinds of electronic test eq, coil testers, Magneto testers, condenser testers, and real world test when all is said and done is too sub with a know good part and quit farten around.
When I find something bad/intermittent/erratic especially electronic ignition module systems for instance I replace it or sub with know good one and quit FARTING around wasting time.
and I'm a electronic tech, electrician, mechanic.