I believe these are the actual photos of Sinn D3-System crown. The photos appeared at website in 2010 and I found long time ago. I was very curious about crown design at that time so I saved the link.
The case looks like an engineering prototype for me. Case back has no sign at all.
[Erledigt] 225,- € Sinn U1000 U 1000 Gehäuse "SUG" fast komplett - UhrForum
Photos credit to original post at uhrforum forum.