The polarity reversing switch was supposed to equalize metal transfer between the points by switching the direction of current flow at every operation of the starter. Eventually, somebody figured out that metal transfer was caused by the capacitance of the condenser being incorrect. The polarity reversing switch was an over-complicated mechanical solution to a relatively simple electronic problem.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!