Back in the days Police bikes were equipped with a button switch on the handlebars which, when activated, triggered a magnetic switch on the side of the speedometer to fix the speed of the preceding vehicle on its own speedometer. Thus, speeding could be recorded as evidence, which was shown to the speeder. On the left side of the dash cover was a button to reset the fixed speedometer needle. Civilian machines were not equipped with this function and the hole in the speedometer cover was closed with this plug.