This is an original coil for a Model T Ford.
One of the many fascinating design aspects of the Model T Ford is its ignition system which consists of a separate, easily removed sparking coil for each cylinder and a 'timer' that is driven directly off the end of the camshaft and which selects the appropriate coil for the cylinder that is about to fire. This timer is vaguely similar to a more conventional distributor, except that it is operating at low voltage rather than at spark plug voltage as in a Kettering system (which is simply the much more familiar high tension distributor with points) or a high tension magneto. One other major difference is that both the Kettering distributor and high tension magneto need to be moving (I.e. the engine must be turning) for any spark to be generated. The Ford 'T' coil, when selected by the timer, will give a continuous shower of sparks. This has the advantage that if the engine is really worn and has little compression, there is a good chance that it will still run.
During the years when the Model T Ford was very commonplace, the coil was known by many names (some not very polite when they were misbehaving) but the most common of these is 'buzz' or 'trembler' coils.
