Checking polarity on a Blaupunkt

[carl cuchetti + susan wayne <cuchetti@xxxxxxxxxxx>]

I am trying to install a Blaupunkt Frankfurt into my 6v '67 1600. I figured out how to switch the voltage from 12v to 6v by pulling out the voltage tab and flipping it aound to the 6v side, but now I need to verify that it's set to positive ground. 
Has anyone done this or know where to go for the info?

Thanks,
Carl Cuchetti

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