I think that is an ordinary kill switch, Blue. Hence it shorts out the ignition system when it makes contact. Grant (willingworker) was still running a Magister on his usual mower a few months ago, and using that copper strip as the kill switch, as he had always done.
You might try checking continuity and earth leakage of the transformer (HT coil). Use a megger for the earth leakage - they test at around 300 Volts, which is much lower than the service voltage, but makes more sense than using an ordinary DMM as a test on a High Tension coil.
