This leaflet from 1979 shows the SP extras pack, designed to allow customers to individualise their Princess and the extras were fitted by dealers.
This is the later version of the Princess SP. The garish SP side stripe is replaced by a subtler Special decal, and there’s a Webasto style sunroof in lieu of the glass one and the fog lights and mud flaps were gone. Inside, the seats were piped in a contrasting colour. These special models were built at the factory.