West Germany Wrist Mileage Device

This is really strange wrist instrument. I'm not sure what I will do with it, but first I would like to find out just what it is, and how it works. It looks like a device for measuring distance in miles. It's not a "pedometer," a device to tell how far you walked. There's no internal pendulum or rotor, and there's nothing to indicate it's operated by the movement of the wrist. Instead, it has a knurled wheel at the lower left. Turning this wheel will cause the single hand to move forward. Is this wheel supposed to be rolled over a map, to determine how far apart two points are? The different color rings are for various scales, that much is certain, with the orange corresponding to the "25" scale (25 miles per inch of map maper?), the blue for "23 etc. More...

Here you can see the wheel. The tines are quite sharp actually. Watch has fixed lugs and the case is a poor base metal with a fairly poor chrome plate.

The "movement" is a simple meshing of wheels, which cause the hand to manually move, as the outer exposed wheel is turned. Is this some sort of German Boy Scout toy? Is it real? What exactly is it. If anyone knows, please let me know. Few more pictures below.

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[I have since been told this is called a "planimeter," and that Hamilton made one for the US military, at some point. Do you think I'll ever use this? I kind of doubt it, but it looked cool, and cost me just a couple dollars.]