That button looks like the starter button that was on my '45 Mack when I got it. I changed it over to a push button on the dash and a Ford solenoid. As for the Tach,I agree the truck was probably used frequently to run a drive belt off the rear wheels for some sort of power tool or a generator (Seems like there would be a locking throttle cable somewhere near it,accessible from outside the truck,but ???).
Speed
