^ This brown wire may have been a hack to bring power from the alternator output directly to the ignition terminal. I'm guessing this because one end (near the alternator?) is broken and read 6 Volts sugesting its attached to the other wires at 6 Volts. Attached to the alternator output, it would have been full voltage.
So if I'm correct about the brown wire, that hack that would mean the field and ignition were always powered, even with the ignition switch off.