Zeke, a majority of the pictures in this thread are of the Yellow Bird CTR-esque cars. The BTR is just another flavor of RUF cars. They continually developed their cars to follow the intruduction of the 911 models....the BTR you posted is the 964 based BTR....B is something about Group B something or another..it's late and I don't recall it all right now.
Here is where you'll find some history and follow the development of RUF cars..
http://www.ruf-automobile.de/english/index1.htm
Go to "About Us" then "History"