E9 GS tuning
Congrats to a very interesting E9,
If I remember correctly Autohaus Gerhard Schneider was/is a BMW Niederlassung (pls correct me if I'm wrong). They are a BMW dealer that sell standard BMW to customers. In addition, they run the GS-tuning company at the time (sold).
The BMW certificate only says the 3,0 CS car was delivered to Autohaus Schneider, which is normal as they are a BMW dealer.
It's very good that you are in contact with the person who build your car. He can verify it, as GS cars are very, very rare.
Cheers
Henric