Evilroy: I seem to have missed this topic first time around, but I suspect that what you're after is this, as fitted on the RAF's VC10 C Mk 1 and Belfast aircraft on first entry to service in the mid-1960s. I was not aware of its being used elsewhere, but I stand to be corrected on that.
As you can see, it had both TwinTrack and Lat/Long displays. On the VC10 it was fed by True Airspeed (TAS), Decca Doppler 62 and a US-made Polar Path gyro-magnetic compass system. (Sorry, the maker's name has slipped after some 40+ years, and I forget the Belfast inputs, though I'm sure it was a Smiths compass system, as part of the overall Flight system.)
I believe that the GPI7 was removed from the VC10 during later system updates, but I can vouch for its still being in use in 1978. I also seem to recall that it was said to be the single most expensive item on the flight deck - other suggestions may be available.