Re:
It's not a 96. Looks like a 98. Note the similarity of the fonts of the decals, in these images. A 98 GT Bravado and a 98 Zaskar.
It could be a 16" or 18". Your friend should probably try it in person.
Mid-to-late 90's, GT's have a great geometry imho. Naturally, the geometry of these frames is aggressive and sporty. Your ass is higher up than the handlebars, and you get into this low, focused, aggressive stance. I love it. However, the more seatpost you use, the more uncomfortable this position becomes. I am 6'1" with long legs, and could not fit comfortably on an 18". Had to use alot of seatpost, and even with 2" riser bars, it didn't work. The angle from saddle to handlebars was too sharp, and it hurt my neck. For GT's, I think it is very important that you fit the frame, without using excessive seatpost.
The head tubes for the 16" and 18" are small. (Not the case for a 19" or 20" though). The top tubes are also short. Yet the seat tube is tall relative to the frame. For someone like me, with long legs, and a small torso, this was excellent geometry. A 19" GT frame, with a 1" or 1.5" riser bar, was perfect for me.