The double advantage of this design is the retraction of the "Magnet ray" caused by the position of the coil's north pole behind the four crossed magnets.
Not only would the coil shunt the axial field, but any portion of the ray projected by the four crossed magnets would be reversed by the attraction to the north pole from behind.
Additionally, the strength of the magnet ray would be amplified by the pole reversal.
Not only would the coil shunt the axial field, but any portion of the ray projected by the four crossed magnets would be reversed by the attraction to the north pole from behind.
Additionally, the strength of the magnet ray would be amplified by the pole reversal.