Coil Voltage

^^Actually the oscillations "are there" during the firing time as well. If you pull a coil wire "open" you get a very very high voltage spike and very high oscillations during "what would be" the firing time, and then finally petering out. this is known as "ringing" (like a bell). It is cause by the exchange of energy between the capacitor (condenser) and the inductance of the coil. They form a resonant circuit, the coil crashing it's inductance which charges the cap, then the cap discharges back into the coil primary, back and forth

"The usual company line" about condensers/ capacitors in the old points days was that they "keep the points from burning." This is true, but the fact is, that they increase spark energy out of the coil. Without a cap, old school ignition systems will normally not start or run.