That's probably someone's attempt to compensate for a poor ground at the vacuum advance unit, which is normally how the distributor housing gets its ground for the points. Look closely at most advance units and you'll see a small copper piece that maintains a good electrical circuit as the housing moves in relation to the engine block. The one year distributor that used a polarity reversing switch (1947, maybe?) would need to have the breaker plate grounded if the polarity switch was bypassed.
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!