Bobson you are right about putting off the compass purchase until you've taken the course.
The M3D is a quality compass by a very good manufacturer, but it lacks some very useful features.
For one, it doesn't have as long a baseplate as featured on the flip-cased and mirrored Suunto MC-1 series, or the flip-cased mirrored Silva Ranger 15 series.
The flip case, when fully open, provides a sufficiently long baseplate that you can more easily plot bearings from map to field, or vice-versa, no matter the scale of your map. With a 7.5 min scaled quadrangle map, it is very easy to 'run out' of baseplate. This means the short-ish plate may not span two widely spaced map features in a single manipulation. In mountain country, you might be sighting over an intermediary ridge(s) to a more prominent known feature (think Half Dome, or Looking Glass Rock) that you can clearly see two ranges over. But you can't span this expanse of ground with your compass' short baseplate without having to fumble and reset, which reduces the accuracy of your plot. Small angular errors have a way of piling up the further out you are.
The flip-case also shields a mirror, which is a very useful feature when you want to take accurate sight bearings. You flip the cover open such that while sighting through the cover's top edge notch you can see a reflection of the compass bezel and underlying bezel base. Turn the bezel ring so the bezel base matches up its red/reflective arrow with the bezel's red/reflective magnetic needle. Read the resulting bearing in degrees at the registration point, which is at the top of the compass centerline.
The best flip-case compasses also have a declination adjustment screw, which allows you to pre-correct your compass for the local magnetic declination. iirc, declination can be as much as +20 degrees in CONUS, which adds up to a lot of on-the-ground error unless you account for it. Without the adjustment screw, you will have to remember -for each reading- to add or subtract declination, depending on whether you're working from map to compass, or compass to map. This is not hard math, but when tired and cold it is easy to add rather than subtract 17 degrees easterly declination (as in Snohomish county), so the error on the ground becomes 34 degrees = humongous.
The very best flip-case compasses also feature an inclinometer scale, which allows you to measure the angle of the ground relative to horizontal. Slope angle is a very useful piece of info esp. when skiing in avalanche country.
Sorry for droning on.
edit: corrected to inclinometer.