GG is Sandoz generic imprint; V is for Qualitest. Both are generics, both are the same potency.
When comparing Watson generic Norcos to Qualitest generic Norcos, I've noticed that the Qualitest are much harder(harder to break in half, etc) and the effects seem to come on more gradually, yet last longer. In contrast, the Watson's are easy to break, work quickly, but drop out quickly too.
Perhaps the Qualitest Xanax is formulated in a similar way that makes it pseudo-time release, especially compared to the Sandoz(which I myself have as well), which dissolve easily and work very quickly.