UPDATE AT BOTTOM
In today's Federal Register, there's a notice of proposed special conditions for single occupant side-facing seats in a new twin-engine 99,600lb business jet that I've never heard of - the GVI.
It very well could be that the FAA was mistaken, and meant to say G650, which is Gulfstream's latest and largest aircraft, set for certification later this year.
...is Gulfsteam perhaps "feelin so fly like a G6", hanging its star on the popular Far East Movement song...
Adding to the Roman number mystery, the company last summer put in a trademark application for yet another Roman numeral aircraft...
UPDATE: Some info provided by Gulfstream on 4 January 2011:
The certification nomenclature for the G650 is the "GVI". They are the same. Just like the GV-SP is the G550 and the GIV-X is the G450. The special condition you mentioned is for a single-person, side-facing seat. Since a customer may choose that as an option on the G650, we wanted to have the approval ahead of time. The seat can be located just about anywhere in the aircraft cabin.