James, you probably first noticed the dial is calibrated in mils,(0-6400) instead of degrees. There is an adjustment screw on the left side that moves the scale. When looking at a topographical map you will find a "GM" (grid to magnetic) conversion graphin the legend, telling you what change to apply to the compass for that particular map's location. This permits accurate navigation without having to figure the GM angle every time you consult the compass. It is calibrated in mils rather than degrees for artillerymen. This particular compass also allows for measurement of "site to crest", determining the lowest angle at which artillery may be safely fired from a position. In a former life I was an Artillery Gunnery Sergeant, hence my rant. Love the knife, and the compass!