The Model T Ignition Coil
Part I: The Ford/K-W Ignition Company Story
By Trent Boggess and Ronald Patterson

The jump spark system employed a spark
plug, a commutator that timed the spark to the
cylinder, a battery to serve as a source of current,
and a vibrator coil. (See Photo 1). The theory of
the vibrator coil was quite complex for the time.
It consisted of two circuits of wires wound around
an iron core. (See Photo 2). The primary circuit
consisted of a number of turns of fairly heavy
gauge wire. When current from the battery
flowed through this circuit it served to turn the
iron core into an electromagnet. The seondary
circuit consisted of a very large number of turns
of a very fine wire wrapped around the same iron
core. This secondary circuit was connected to the
spark plug. When the primary circuit was broken,
the magnetic field around the iron core
collapsed, inducing an electrical current through
the secondary circuit. Because of the large number
of turns of wire in the secondary circuit, a
very strong electrical voltage was induced in it.
While brief, this high voltage was sufficient to
jump across the gap between the electrodes of the
spark plug and ignite the fuel-air mixture in the
cylinder. The term vibrator coil arose from the
use of two electrical contacts and a spring arrangement
to close and open the circuit between
the battery and the primary circuit. When the
primary circuit was closed and the iron core was
saturated with magnetism, the spring would be
attracted towards the iron core, separating the
contacts, and thus breaking the primary circuit
Once the contact was broken, the magnetic field
collapsed, inducing a high voltage in the secondary
circuit that would jump the gap at the spark
plug. At the same time, the collapse of the magnetic
field released the spring allowing the contacts
to touch and reestablish the primary circuit
and thereby start the entire process all over
again. This continuous making and breaking of
the contacts resulted in a vibration or buzzing of
the coil and an accompanying stream of sparks

It looks like 3 coils...two secondaries, and one primary.  And the secondary and primary are joined at the condenser???

This may be off topic but since John B is here, I thought that I'd ask.

I have heard of a WWII earth battery that was capable of very high amp outputs. But I can not (through extensive searching on the internet) find any info on this earth battery. As though all reference has been removed. To my understanding it employed a 4' x 4' x 1/4" lead plate and I believe mercury. I know that the mercury battery was invented during WWII, but I do not believe that this battery was galvanic because of the reported output.

I believe that this groups reason for replicating the Stubblefield is because it performed way better than other earth batteries. But if this other battery worked as well as claimed, then I would like to have more information on it so that the processes of the two batteries can be compared. They may both operate on the same principles.

It may have had a specific name which is why I can't located any info, diagrams or pictures. Does anyone here have any info that they can share?

And then there is this from:   http://www.modeltcentral.com/Model-T-Ford-Electrical-Specifications.html

Ignition Coil

Each Model T Ford runs using four coils, one per cylinder, housed in a coil box that features contact points for a power supply in, contact point to the timer for each coil via a wiring loom and a contact terminal for the spark plug lead. The style and location of coil boxes changed throughout the years the Model T was produced, but all do the same thing (with the early models including the ignition switch)

Each coil assembly is housed in a finger jointed timber box, filled (originally) with tar or pitch as its also known. This tar, not only holds the components in place, but adds to waterproofing and insulating the parts from each other. The parts inside include a primary coil winding, a secondary coil winding, a condenser, connecting wires and a piece of glass to divide the components.

PolishPunisher do you mean this?:
In World War II, the only commonly available dry battery was the carbon-zinc cell, which suffered greatly in the high temperatures and high humidity of some theatres of operation. The search for a better battery succeeded in 1944, with the invention of the mercury dry battery. This battery could not only resist the high temperatures and high humidity, but also had better discharge characteristics, longer shelf life, and greater efficiency.

The excellent mercury battery, and to a large extent the nickel-cadmium cell, have been suppressed because of the mercury and cadmium they contain, which are a hazard with unwise disposal of used batteries. Since it is easier to legislate the batteries out of existence than to control disposal in the face of a careless and ignorant population, this has been done.

The mercury battery has a cathode of HgO depolarizer, a KOH electrolyte, and an anode of amalgamated zinc powder. It is essentially an alkaline cell with a different and more efficient cathode. Like the alkaline cell, it is sealed in a steel case to prevent leakage of the corrosive electrolyte. The open-circuit voltage is 1.35V or 1.40V, and the polarity is reversed compared to the carbon-zinc and alkaline cells. That is, the central contact is negative, not positive, and the case is positive, not negative. The mercury battery has an excellent efficiency, consuming more than 90% of its chemicals before its terminal voltage drops substantially, when used at a current of 100mA per square inch of depolarizer surface. A typical AA size cell can take loads of up to 200 mA, either intermittent or continuous, and has an output of 2400 mA-hr, about twice that of a comparable carbon-zinc cell, and considerably more than an alkaline cell. The output voltage is quite constant, and the shelf life is long, so the mercury battery is superior. The silver oxide cell is similar, using an Ag2O depolarizer, a KOH or NaOH electrolyte, and the usual zinc anode. Its output voltage is higher, 1.5V, and so is its cost. Silver cells come only in the button size.

These cells all burn zinc to zincate, and get their energy from this reaction. Fuel cells are another chemical source of electrical energy, and not a new one. They have been around for over a century, but have always proved noncompetitive because of their size, weight and expense. They burn things like alcohol or natural gas, to water and carbon dioxide, like any fire. Fuel cells are now being developed for military use, where cost is no object. These seem rather larger and heavier than batteries, but of course they can be used continuously and replace lots of batteries if you keep feeding them alcohol. It is difficult to believe that they will ever be cheap and convenient enough to replace zinc burners.