Originally Posted by Xtremjeepn
Cool! So does it must have some way to set a scale first.
This is called the Map Meter. When I first found these a few years ago, I did end up seeing the Mile Marker, but I couldn't find one when my wife asked me what I wanted for my birthday.
The scale is set to 1:50000 and if the map is at that level, then you read directly from the inner dial the number of kilometers. In the owner's manual, there is also the conversion chart to understand how to change it.
It's largely a gadget these days, but I think a really cool idea.