Bob Moore wrote:
A Ground Instructor Certificate can have any of three ratings:
Basic, Advanced, and/or Instrument
No such thing as an AGII. Advanced and Instrument are two
separate ratings. The Advanced rating is not required in order
to provide instrument training, just the Instrument rating.

Bob Moore
Ground Instructor Certificate
Advanced Ground Instructor Rating
Instrument Ground Instructor Rating

Yes, I stand corrected on the phraseology. I also hold
an AGI with an Instrument endorsement. I've just always
called it AGII ... sortof like CFII.