Yes, you are absolutely right, it is a 1964 GTS 904. Thanks for the additional information.
This road-legal racing sports car was used, among other things, as a camera car for "Zweites Deutsches Fernsehen" at the 1000 km race on the Nürburgring in 1966 (picture 4).
One 904 even received an 8-cylinder engine, type 771 (picture 5).
Congratulations on your next point.