That is the key code for your specific car. Unscrupulous people can make a key to your car with that info.
Your car is a 280 SL and has a two sided ignition key, therefore, from the factory, your gas cap would open with that same two sided key.
Your gas cap is not original to your car.
I apologize if this is obvious, I did not study the entire thread.
Enjoy the ride.
Mark