When I was taking my navigation and pilotage course, we had to learn about plotting courses with a magnetic compass. Even in the '80’s, there was a lot of disbelief that the Powers That Be felt it necessary. Nonetheless, we had to laboriously create a separate heading for each track for magnetic compass readings (taking into account the ship’s magnetic affect on the compass, called the deviation). And, of course, even though the ship actually did have an official magnetic compass, it was corrected for the deviation. But by Og, if we were ever required to plot a course using only hand-held magnetic compasses, then we were ready!
I always thought the whole thing was cool in a “Roots” kind of way. I’ll admit that I was never called upon to fiddle with the things or I might have a different attitude.