And by GSE, I mean Ground Support Equipment.
I was in ATL on Tuesday and sat at my usual spot in the food court in Terminal B. With a good overview of Ramp 2, I listened to the ramp controller and watched his puppet show. Plenty of good moves, and enough laughs to make the time pass by. The other interesting thing of this spot is watching the ground equipment move about at the intersections. Even more laughs out of them. As I was watching them I noticed that all the tugs had an ID on them. I'm not talking about the equipment number, I'm talking about the letters. Usually located on either side of the front, and then also either side of the back. Here is what I spotted:
the most common letters...
BR (sometimes in combination with DOM)
z-numbers: (these were the letter Z with a superscript of a number to the right of it)
7z (a 7 with a superscript of a Z)
Also there were a few that said PIER and then a number.
So basically you can figure out the question: what do these all mean?