In reply to Mark Kemball:
> Similarly, what is the function of the depression left of the direction of travel luminous mark?
This is where the radioactive sign goes on the military version. You can see it in the smaller picture in the link you sent.
> How does one use the E and W declinations on the base plate?
When taking a bearing, you can line the end of the needle up with a point (say, 2°W) on those declination scales then (if that was the right declination) your north-south lines on the bezel would be ready for the map.
For going map-to-bearing, can either again align the needle with the point on the scale, or line it up with the point then rotate the bezel over (without turning the entire compass) to line with the normal arrow.
I'm not doing the greatest job of explaining, best to experiment with it a bit! Hopefully you get the jist of it.
I never use it, as my inability to walk in a straight line is far more significant than the current declination.
