Sea urchin? Molar?

[Ivaldir]

I found this two years ago at the North sea (Maasvlakte  2 in the Netherlands) at sand suppletions. It's known for finding megafauna mostly mammoth and rhino. The finds on the beaches are early Pleistocene to Holocene, depending on where the sand was gathered (it's pumped from kilometers in sea). Rarely, older pieces can make their way there by rivers.

I can't figure out this piece, even if it is fossil or not. Hopefully someone can help. Length is 5 cm.

[Rockwood]

The top photo appears to show two gastropod shells. The other side may be bryozoan.