that one is the guid of Enemy Territory.
you can find an explanation about it when you launch q3fill with the -B ? option:
Code:
-B G P support for "Enemy Territory 2.60 + PB" servers
you must specify the game's CL_GUID and the PB_GUID you want to use.
these parameters are visible in the "connect" packet sent from your
real game client to a server and are based on the content of the file
etkey available in the game folder.
When you connect to a server your client authenticates on the auth
server, so try to use this -B option after having connected to a host
with your real client (or you will receive an error message or none).
Knowing your GUIDs is extremely simple:
- download the "Quake 3 engine testing server" tool:
http://aluigi.org/testz/q3ts.zip
- double-click on the q3ts executable, it will be launched immediately
- open your ET 2.60 client (with Punkbuster enabled, pb_cl_enable)
- from the console type "connect localhost" or connect to localhost
or 127.0.0.1 through the usual "Play Online -> Connect to IP"
- in the window of the testing server tool you will see the plain-text
"connect" packet with all the needed fields (cl_guid\G and *P)
Sorry, but I don't have time and desire to make something better