My only...teeeny ctitique... would be the term magnetic "declination"
If you thou still use "thou" in everyday speech..be happy.
The term magnetic *variation* however has been around for at least few tens of decades.
(There is an old navigator's maxim "variation East, compass least, variation west, compass best"....but I also have *very* old compass that belonged to my great great grand father that is inscribed.."East or west, home is best" )
Despite my pedantry...A well written piece!
