So... The story behind this one is that as we were on our way to Travemûnde, we stopped by this beach/cliff, about 20km north of said town. I think that area is called Brodtener Steilufer.
I saw this little concretion and decided to whack that on to another rock, and this little thing popped from there. No single idea what it could be. It is quite fragile (I accidentally brushed almost all material in other half away...). And as it can be seen, small one too. No idea of the age or any other metadata. BUT according to one site, near by is sites where Cretaceous, Silurian and Ordovician material can be found.