Nailed to the passenger side bottom outside seat riser. Same place as the Roadster and Phaeton. The exact location varies depending on the worker that installed it. The Filling Station
www.fillingstation.com sells a reproduction as will as others.
If you have one I would appreciate an email or PM with information on it. Guess I will again try to update my list of owners that I started 40+ years ago and have let lapse for way too many years.