I picked up a 50's-60's Mallory 6 volt coil that will compliment nicely with the old school dual point Mallory distributor I"ll be installing over the winter. Since this coil has no instructions with it, I have a simple question: On the negative terminal there is what appears to be a chrome plate covered, hockey-puck-shaped resistor with the number "30" stamped on the attachment plate. The resistor's purpose? For further identification, on top of the coil adjacent to the positive terminal screw is the wording...VOLTMASTER 6 V.