The switches for '47 and '48 are different in that they are an Off-On-Off configuration. The left key position is Off and locked, needing a key to unlock. The right position is Off but unlocked, and the key can be removed from the switch. There is a lever on the switch allowing you to move between the Off and On position after removing the key. The advantage of this is that the On position can be accessed without needing to have a key with you, which I'm sure was a feature much appreciated by the farmer who walked out to the truck in the lower 40 and found he left the key back in the barn.
