Uli,
I will have to wait for other members to weigh-in and comment for Germany frame head tube stickers. I have many U.S. CB750's and all mine have riveted data plates but the Sandcasts. Attached picture is what the US aluminum Sandcast frame head sticker looks like up to 9/69.
The head tube sticker or riveted data plate is located on the right side opposite of the VIN stamp (on left).
I have seen the sticker you are showing on US CB & CL 450 and 350 models, but never as CB 750, but my newest bike is a 1976 model year.
Hope that helps,
DW