The distributions of the electric and magnetic fields and power of the classic rectangular waveguide twin-slab ferrite phase shifter, with one region magnetised along the positivey-direction and the other along the negativey-d irection, are re-examined in the paper. It indicates that this type of device may quite often be phenomenologically described by a nonreciprocal edge-mode effect, rather than, as is customary, in terms of circular variables. This model may be of value in the design of practical wideband devices. The presence of counter-rotating magnetic fields at the two open faces of the ferrite region is also of note. The use of unequal oppositely magnetised sections is a possibility that has not received any attention so far.