The coil you're playing with is part of a system called "waste spark". It's
designed to operate on two cylinders that are 180 degrees out of phase and
sparks both of them in series at the same moment with the block (engine
ground) in the middle. Effectively one cylinder is at the top of the
compression stroke and the other is at the top of the exhaust stroke -
hence the "waste". It was an early form of DIS (distributorless ignition
system) and represents a compromise as it saves half the cost of a coil per
cylinder (which is much more common now) There was a moment in history when
it was common to "rotate" your spark plugs to get longer life out of them.
(put them in the opposing cylinder to get the spark polarity reversed)
Electrically, I believe that means that both of the high voltage terminals
you have can be expected to float relative to system ground. Actually,
thinking about it, I wouldn't be a bit surprised if they have some internal
center tap in the secondaries back to the primary to keep it from floating.
Perhaps even a high impedance connection. Two minutes with an ohmmeter
would tell much.

-Denny
--=20
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